JP2021119437A - Data management system, data managing device, spontaneous movement condition determination device, spontaneous movement destination selection device, archive instruction device, and data management method, and program - Google Patents

Abstract

To store data without deletion even if a storage capacity of a storage device is in shortage.SOLUTION: A data managing device 1 (1A) of a data management system 1000 (1000A) has a hot storage and a cold storage. The data managing device 1 moves spontaneous movement object data determined to satisfy a predetermined spontaneous movement condition regarding access of data by a spontaneous movement condition determination device 21 to a spontaneous movement destination node that is in a position in which communication costs of a user terminal are reduced and selected by a spontaneous movement destination selection device 22. The data managing device 1 receives instruction information for moving data having the minimum availability evaluation value from the hot storage to the cold storage from an archive instruction device 23 and executes it.SELECTED DRAWING: Figure 8

Description

The present invention relates to a data management system, a data management device, a spontaneous movement condition determination device, a spontaneous movement destination selection device, an archive instruction device, a data management method, and a program that control data arrangement in distributed storage.

Conventionally, a cache control technology is known as a technology for deploying data to a data storage location (storage) in a location convenient for a terminal or application (hereinafter referred to as "user terminal") that accesses data. The characteristics of the location (convenient location) selected as the data storage location include, for example, a location with good Quality of Service (QoS) defined by the presence or absence of delay, and a location with low data transfer energy such as being physically close. Can be mentioned.

The cache control technology provides a function of temporarily storing data used by a user terminal near the user terminal, assuming the characteristic of the locality of the user terminal (mostly accessed from the same location). This temporarily stored data is called cached data and is a temporary copy of the original data. On the other hand, the storage capacity is finite, and cache data that seems unnecessary is deleted. LRU (Least Recent Used) and TLRU (Time aware Least Recent Used), which are called replacement algorithms, are known as algorithms to be determined to be unnecessary (see Non-Patent Documents 1 and 2).

LRU is an algorithm in which the last part of a data string arranged in order from recently accessed data is deleted. Further, the TLRU is an LRU in consideration of TTL (Time To Live) and TTU (Time To Use). The TTL indicates the limit of time that the data can exist in the cache, so to speak, the expiration date of the data. Since the original data may change over time after the cache data is generated, the correctness of the data is guaranteed by setting the TTL. In addition, TTU indicates the limit of the time that the data can survive from the time when the data is generated, so to speak, the expiration date of the data.

Kai Cheng et al., “LRU-SP: A Size-Adjusted and Popularity-Aware LRU Replacement Algorithm for Web Caching”, Proceedings 24th Annual International Computer Software and Applications Conference. COMPSAC2000, IEEE, October 2000 Giovanni Neglia et al., “Access-time aware cache algorithms”, 2016 28th International Teletraffic Congress (ITC 28), IEEE, September 2016

In the above-mentioned conventional technique, for example, data is stored in the order of input in the storage device, and when the storage capacity is full, the data (old data) at the beginning of the data string is deleted and newly input. The data is stored at the end of the data string. When the data in the storage device is accessed, the data is moved to the end. In other words, new data and data with the latest access time are treated as important data. However, these indicators are not sufficient as indicators for measuring the importance of data.
Further, in the above-mentioned conventional technique, when the storage device is full, only data can be deleted from the storage device, and inconvenience occurs, for example, when there is data that should not be deleted even if it becomes old.

The present invention has been made in view of such circumstances, and an object of the present invention is to store data without deleting it even when the storage capacity of the storage device is insufficient.

The data management system according to the present invention is a data management system including a data management device which is the node in a storage network composed of a plurality of nodes functioning as storage devices, and the data management system stores data. It is provided with the data management device having hot storage and cold storage for the data, a spontaneous movement condition determination device, a spontaneous movement destination selection device, and an archive instruction device connected by using the data management device as its own node. The spontaneous movement condition determination device determines that the data is the spontaneous movement target data when the data stored in the hot storage satisfies a predetermined spontaneous movement condition regarding access to the data, and the spontaneous movement destination selection device. Indicates a node to move to a node other than the own node, which is located at a position where the communication cost of the user terminal when accessing the data is reduced, from the node holding the data to be spontaneously moved. The archive instruction device selects the data stored in the hot storage of the own node as the destination node, and the own node selects the data having the smallest usefulness evaluation value, which indicates a higher value as the prediction of the number of future accesses is larger. The instruction information to be moved to the cold storage is transmitted to the data management device, and the data management device moves the spontaneous movement target data to the spontaneous movement destination node, and when the instruction information is received, the hot of the own node is received. It is characterized in that the data having the minimum usefulness evaluation value stored in the storage is moved to the cold storage of the own node.

According to the present invention, even when the storage capacity of the storage device is insufficient, the data can be stored without being deleted.

It is a figure which shows the structure (tree structure) of the storage network which concerns on this embodiment. It is a figure for demonstrating the outline of spontaneous movement in the configuration (linear connection) of the storage network which concerns on this embodiment. It is a figure which shows the whole structure of the storage network including the data management system which concerns on this embodiment. It is a figure for demonstrating the details of the function of the spontaneous movement processing unit which concerns on this Embodiment, and the function provided by each apparatus concerning spontaneous movement. It is a figure for demonstrating the uneven distribution of access in this embodiment. It is a figure for demonstrating the details of the function of the forced displacement processing unit which concerns on this embodiment, and the function provided by each apparatus concerning forced displacement. It is a figure for demonstrating the process of forced movement in this embodiment. It is a figure which shows the whole structure of the modification of the data management system which concerns on this embodiment. It is a figure which shows the whole structure of the modification of the data management system which concerns on this embodiment. It is a flowchart which shows the flow of the data arrangement control by the spontaneous movement of the data management system which concerns on this embodiment. It is a flowchart which shows the flow of the optimum node selection process of the data management system which concerns on this embodiment. It is a flowchart which shows the flow of the data arrangement control by the forced movement of the data management system which concerns on this embodiment. It is a flowchart which shows the flow of the data generation interval adjustment of the data management system which concerns on this embodiment. It is a hardware block diagram which shows an example of the data management apparatus which concerns on this Embodiment, and the computer which realizes the function of each apparatus. It is a figure which shows the configuration example of the data management apparatus which is the modification of the data management system which concerns on this embodiment.

Next, a mode for carrying out the present invention (hereinafter, referred to as "the present embodiment") will be described. First, an outline of the present invention will be described.

<Overview>
Today, the Internet of Things (IoT) continues to expand rapidly, and a wide variety of devices are being connected to networks. And it is expected that the huge amount of data generated by these devices will be utilized. For example, many surveillance cameras are already installed on the streets and stores to record daily images. In addition, operation data of factories and the like are collected using sensor devices and the like. These large amounts of data are used as big data for various services and data analysis.

Regarding the management method of this large amount of data, especially real-time data (live data), (1) management in the data center, (2) management by the storage network, that is, distributed storage in the network, (3) data generation (3) There are three possible methods: management by the device (Publisher) that collects the data. Among these, (1) in data center management, traffic may be concentrated near the aggregation point, causing network congestion. (3) In the management by the device itself, since the data storage capacity of the IoT device is usually small, even if it is possible to manage static data other than live data (legacy data stored in the device in advance), It is difficult to store a large amount of live data. On the other hand, (2) in a storage network, it is efficient to hold data in storage (each node as distributed storage) at an appropriate point near the user terminal (Subscriber) requesting data acquisition. Data management can be realized.

In addition, when hot storage, which is a conventional storage method for live data (for example, HDD (Hard Disk Drive)), is difficult to handle due to capacity and cost, cold storage and hot storage can be used together. Conceivable. Here, the "hot storage" is a constantly operating storage medium such as a conventional HDD or SSD (Solid State Drive) that can satisfy real-time requirements. The hot storage is faster response speed for example, 10 ^-8 ~10 ⁰ (s), the capacity is limited, it is costly compared to cold storage. Further, the "cold storage" is a storage medium such as a DVD (Digital Versatile Disc: registered trademark), a CD, a BD (Blu-ray Disc: registered trademark), or the like that cannot satisfy real-time requirements. The cold storage is slow response speed, for example 10 ⁰ to 10 ⁴ (s), the capacitance is very large capacity (can be assumed infinite Increasing the storage medium.), A low-cost compared to hot storage. The response to the request for the data stored in the cold storage is, for example, by physically moving the robot arm, acquiring a DVD or the like stored on the shelf, and setting it in the data reading / writing module or the like. It may be performed by manually setting a DVD or the like in a data reading / writing module or the like.

By equipping each node of the storage network with this hot storage and cold storage, data that is not desired to be deleted even if the access time is long is moved from the hot storage to the cold storage and saved. As a result, highly useful data that needs to respond to real-time requests is stored in hot storage, and less useful data is stored in cold storage without deleting the data. It is possible to keep the memory in the user and improve the convenience of the user.

In this storage network, for example, as shown in FIG. 1, each node of the storage network is connected as a tree structure. Further, as shown in FIG. 2 and the like described later, each node may be linearly connected by a link. The link connecting the nodes (storage nodes) may be composed of a plurality of switches and a plurality of transmission lines, or a small network (called an underlay network).
Then, in the storage network to which each node having hot storage and cold storage is connected, an appropriate node is selected and data is arranged. Here, an appropriate node is, for example, a place where QoS (Quality of Service) expressed by the degree of delay is good (a place where there is little delay) or a user terminal which makes a data acquisition request is physically close. It refers to a node in a place where the data transfer energy is small.

In the conventional data allocation control by this storage network, it is assumed that the following control is executed when the capacity of the hot storage overflows.
(Control 1) Move less useful data from hot storage in a node to cold storage (hereinafter referred to as "archive").
(Control 2) Move highly useful data to an appropriate hot storage of another node.

In the data management system 1000 (see FIG. 3 described later) according to the present embodiment, "spontaneous movement" and "forced movement" are performed by further improving the processing assumed in (control 1) and (control 2) above. Data placement control is performed by "movement" and "adjustment of data generation interval according to real-time request".

[Spontaneous movement]
First, spontaneous movement will be described.
Spontaneous movement in this embodiment means to reduce communication costs when a node exists in a more optimal location for a user terminal (Subscriber) requesting data acquisition than the current data holding node for a certain data. In addition, it refers to a process of voluntarily moving the data to the node (“optimal node” described later).
The above-mentioned (control 2) movement to another node is a process of moving data whose performance can be improved by changing the node to be held when the capacity of the hot storage overflows. This (control 2) is triggered by the timing when the capacity overflow occurs, but in the spontaneous movement of the data management system 1000 (FIG. 3) according to the present embodiment, the capacity overflow occurs in order to improve the performance earlier. Not limited to the timing of occurrence, when the target data satisfies a predetermined condition (“spontaneous movement condition” described later), the optimum node is selected and moved.

Whether or not a certain data is the target data for spontaneous movement is determined based on the "usefulness evaluation value" and the "access uneven distribution".
The usefulness evaluation value is an evaluation value in which the larger the number of future accesses predicted based on the number of accesses up to the present time, the higher the value of the data. The higher the usefulness evaluation value, the higher the possibility that the data will be accessed from the user terminal in the future, that is, the data is highly useful data.
In addition, the uneven distribution of access indicates the uneven distribution of the number of accesses from the adjacent node of the access source to the data held by the node. In other words, for a certain data, the higher the access unevenness of one node among the plurality of adjacent nodes, the more the data is accessed from a single direction, and the current node (holding the data at the present time). It shows that the probability that the node) is a demand point node is low. The demand point node is a node that receives a data acquisition request from a user terminal (Subscriber) accommodated by the user terminal (Subscriber). If the target data is held in the demand point node, the data transfer energy can be reduced, the delay and the like can be reduced, and the QoS can be improved as compared with the case where the data is requested and acquired from another node.

Specifically, as shown in FIG. 2, for example, when each node of the storage network is linearly connected _{, data "A" is stored in the hot storage of node N 10} (current node), and the data "A" is stored. It is assumed that "A" satisfies a predetermined spontaneous movement condition. _{Here, the node N 50} that receives the acquisition request for the data “A” from the user terminal U becomes the demand point node. The data "A" stored in the current node has an uneven distribution of access to the _{node N 20} adjacent to the _{node N 10} (in the direction of the _{node N 50} ) when the access from the _{node N 50 side, which is the demand point node, is large.} It gets higher. Therefore, the higher the uneven distribution of access, that is, the more the data "A" is accessed from a single direction, the lower the probability that the current node is the demand point node, and the more optimal (closer to the demand point node) node (optimal). Indicates that it is worth moving to node N _30).
In FIG. 2, the node N _{30 closer to the demand point node N 50 is} selected as the optimum node by the optimum node selection process described later, and the data “A” stored in the node N ₁₀ is spontaneously moved _{to the node N 30.} An example of making it is shown.
Details of this optimum node selection process will be described later with reference to FIG.

[Forced movement]
Next, forced movement will be described.
When data overflow occurs when trying to store new data in a certain node, as in (Control 1) above, among the data stored in that node, the data with low usefulness (usefulness evaluation value) Can be archived and stored in cold storage. However, if another node holds data with a lower usefulness evaluation value, the capacity overflows in order to hold data with a higher usefulness evaluation value in the hot storage of the own node. Instead of archiving the data with the lowest utility rating on the node, the smallest data with even lower utility ratings on other nodes should be archived.
In other words, in forced movement, when the hot storage capacity of a node overflows, the data with the minimum usefulness evaluation value of that node has the usefulness evaluation value of all the nodes (movable nodes described later) that make up the storage network. If it is not the minimum, the node with the smallest usefulness evaluation value among all the nodes (movable nodes) is selected as the forced move destination node. Then, the data with the minimum usefulness evaluation value of the node whose hot storage capacity has overflowed is moved to the selected forced movement destination node.
Details of this forced displacement will be described later.

[Adjusting the data generation interval according to real-time requests]
Next, the data generation interval adjustment according to the real-time request will be described.
A device (Publisher) that generates (collects) data transmits a set of data generated in real time within a predetermined time to a node as one data group at predetermined time intervals. With respect to the device that generates this data group (referred to as "data" in a broad sense), if the real-time demand (for example, a value proportional to the number of accesses within a predetermined time after data generation) is high, the data By shortening the generation interval, the AoI (Age of Information) of the device can be reduced. Note that AoI means the freshness of information (indicating the elapsed time from the generation time of the latest provided data).
Further, regarding this data (data group), there are data with a large number of accesses and data with a small number of accesses within a certain period of time. If AoI is not taken into consideration for this stored data, storage may be wasted more than necessary. For example, in a device that generates data (data group) with a small number of accesses, if AoI is increased, data having a large data capacity is generated as one data, transmitted to a node, and stored in hot storage. On the other hand, for example, if the generation of a data group (data) in a 60-minute cycle of a certain device is generated in a 10-minute cycle, the data capacity of one data can be reduced. Therefore, the transfer energy (network load) for moving the data can be reduced. As a result, it is possible to reduce the number of links excluded from the use of data movement and increase the number of movable nodes (details will be described later) that are candidates for the data placement destination (optimum node) in the present embodiment.
Therefore, the latest data of a device with high real-time demand adjusts AoI to be smaller, that is, to shorten the data generation interval. On the other hand, the latest data of devices with low real-time demand adjusts AoI to be larger, that is, to increase the data generation interval.

Hereinafter, the data management system 1000 and the like according to the present embodiment will be described.

<The present embodiment>
FIG. 3 is a diagram showing an overall configuration of a storage network including the data management system 1000 according to the present embodiment.
As shown in FIG. 3, the data management system 1000 includes a data management device 1, a spontaneous movement condition determination device 21, and a spontaneous movement destination selection device 22, which are a group of devices used to realize the above-mentioned “spontaneous movement”. The archive instruction device 23, the forced movement target data selection device 31 and the forced movement destination selection device 32, which are a group of devices used to realize the above-mentioned "forced movement", and the above-mentioned "data generation interval adjustment". It is provided with a generation interval adjusting device 40 used for realization.
The data management device 1 is each of the above-mentioned nodes that functions as a storage device in the storage network, and includes a finite capacity storage unit 100 composed of hot storage and an infinite capacity storage unit 105 composed of cold storage. Then, the plurality of data management systems 1000 are connected via the network to construct a storage network as a whole.

The spontaneous movement condition determination device 21, the spontaneous movement destination selection device 22, and the archive instruction device 23, which are a group of devices related to spontaneous movement, are provided for each data management device 1, and are provided between these devices and in the data management device 1. Communication connection is made.
The forced movement target data selection device 31 and the forced movement destination selection device 32, which are a group of devices related to forced movement, are provided for each data management device 1, and communication connection is made between these devices and to the data management device 1. ..
Further, the generation interval adjustment device 40, which is a device related to data generation interval adjustment, is provided for each data management device 1, and is communicated and connected to the data management device 1 and a device (Publisher) that generates data.

The spontaneous movement condition determination device 21, the spontaneous movement destination selection device 22, the archive instruction device 23, the forced movement target data selection device 31, the forced movement destination selection device 32, and the generation interval adjustment device 40 are a control unit, an input / output unit, and the like. It is composed of a computer equipped with a storage unit (all not shown). When each device needs the state information described later of each data management device 1 in the processing performed by itself, each device refers to the state information stored in the storage unit 12 of the data management device 1 connected to itself and processes the data. To execute. A detailed description of the functions provided by each device will be described in the detailed description of the data management device 1.

≪Explanation of data management device and each device≫
Next, with reference to FIG. 3 and the like, the details of the data management device 1 and each device related to "spontaneous movement", "forced movement", and "data generation interval adjustment" will be described.
The data management device 1 stores the data from the communication-connected device (Publisher) P in the hot storage (finite capacity storage unit 100), and colds the data from the hot storage (finite capacity storage unit 100) as needed. An archive that moves data to the storage (infinite capacity storage unit 105) is executed. Further, the data management device 1 performs more appropriate data arrangement control by performing the above-mentioned "spontaneous movement", "forced movement", and "adjustment of data generation interval according to real-time request" in cooperation with each of the above-mentioned devices. conduct.
The data management device 1 includes a control unit 10, an input / output unit 11, and a storage unit 12.

The input / output unit 11 inputs / outputs information to / from another data management device 1, each device (Publisher) that generates data, a plurality of user terminals (Subscriber) that it accommodates, and the like. Further, the input / output unit 11 communicates with each device (spontaneous movement condition determination device 21, spontaneous movement destination selection device 22, archive instruction device 23, forced movement target data selection device 31, forced movement destination selection device 32). , Information is input and output to and from the generation interval adjusting device 40). The input / output unit 11 is composed of a communication interface for transmitting and receiving information via a communication line and an input / output interface for inputting and outputting information between an input device such as a keyboard (not shown) and an output device such as a monitor. It is composed.

The storage unit 12 is composed of a hard disk, a flash memory, a RAM (Random Access Memory), a data reading / writing module, and the like.
The storage unit 12 (storage means) includes a finite capacity storage unit 100 composed of the hot storage described above and an infinite capacity storage unit 105 composed of the cold storage described above.
Further, the storage unit 12 further contains information on an access source (other data management device 1 or user terminal) and the number of accesses to the data stored by itself, and information on the storage capacity of the other data management device 1 (hot storage). Information such as free space), connection status with another data management device 1 (for example, link usage) (hereinafter, these information are collectively referred to as "state information") and the like are stored. When links are used in the network configuration of each node of the storage network described above, statistical values such as the total usage of each link and the average usage of each link are used as the usage status (state information) of the links.
Then, the storage unit 12 stores a program for executing each functional unit of the control unit 10 and information (predetermined threshold value, etc.) required for processing of the control unit 10.

The control unit 10 controls the overall processing executed by the data management device 1, and as shown in FIG. 3, includes a condition monitoring unit 110, an acquisition request processing unit 120, a spontaneous movement processing unit 130, and a data storage unit 140. , The forced movement processing unit 150 and the like.

The status monitoring unit 110 includes an access source for each data of each data management device 1 and the number of times of processing thereof (the number of accesses "A" described later), a usage status of a link between the data management devices 1 (link usage amount), and each. Information (state information) such as free capacity of the finite capacity storage unit 100 (hot storage) of the data management device 1 and data having the minimum usefulness evaluation value is acquired and stored in the storage unit 12.
The state monitoring unit 110 presets from which data management device 1 in the storage network the state information or the like can be acquired. For example, when the storage network is composed of linear connections, it is set so that state information and the like can be acquired from the data management device 1 up to the adjacent N hops (N is a positive integer) (details will be described later). Then, the condition monitoring unit 110 acquires (latest) information of the data having the smallest effectiveness evaluation value among the data stored in the finite capacity storage unit 100 (hot storage) of each adjacent data management device 1. Remember.
Further, the condition monitoring unit 110 also measures the information of the access source and the number of accesses for the data stored in the finite capacity storage unit 100 and the infinite capacity storage unit 105, and stores the information in the storage unit 12.

The acquisition request processing unit 120 receives a data acquisition request (request) from a user terminal (not shown) or another data management device 1 housed in its own data management device 1, and stores a finite capacity in the storage unit 12. The data stored in the unit 100 (hot storage) or the infinite capacity storage unit 105 (cold storage) is returned as response information.
Further, when the acquisition request (request) is not the data stored in its own storage unit 12 but is stored in the other data management device 1, the acquisition request processing unit 120 is the other data management device. Transfer the acquisition request toward 1.
When the acquisition request processing unit 120 receives the acquisition request, the acquisition request processing unit 120 outputs the access source of the data and the number of times the acquisition request has been made (access number “A”) to the condition monitoring unit 110, thereby storing the data in the storage unit 12.

The spontaneous movement processing unit 130 calculates the above-mentioned usefulness evaluation value and access uneven distribution for a certain data. The data to be calculated for the usefulness evaluation value and the uneven distribution of access (hereinafter referred to as "target data") is triggered by, for example, when a certain data receives an acquisition request (request). The data may be used as a calculation target, or each data stored in the finite capacity storage unit 100 (hot storage) may be extracted at predetermined time intervals and used as a calculation target.
Then, the spontaneous movement processing unit 130 transmits the calculated usefulness evaluation value and the access uneven distribution to the spontaneous movement condition determination device 21. Then, when the spontaneous movement condition determination device 21 determines that the spontaneous movement condition determination device 21 satisfies a predetermined spontaneous movement condition based on the usefulness evaluation value and the access uneven distribution, the spontaneous movement processing unit 130 sets the target data as the target of the spontaneous movement. (Hereinafter, referred to as "spontaneous movement target data").
Further, the spontaneous movement processing unit 130 receives the result of selecting the optimum node as the movement destination from the spontaneous movement destination selection device 22 for the spontaneous movement target data, and moves (spontaneously moves) the data to the data management device 1.
Hereinafter, the functions of the spontaneous movement processing unit 130 and the functions provided by each device related to the spontaneous movement will be described with reference to FIG. 4 and the like.

FIG. 4 is a diagram for explaining the details of the functions of the spontaneous movement processing unit 130 according to the present embodiment and the functions provided by each device related to the spontaneous movement.
As shown in FIG. 4, the spontaneous movement processing unit 130 includes a usefulness evaluation unit 131, an access uneven distribution calculation unit 132, a spontaneous movement execution unit 133, and an archive execution unit 134.

The usefulness evaluation unit 131 evaluates the usefulness of each data (target data) as an evaluation value in which the larger the predicted value of the number of future accesses (from the present time to the future) based on the number of accesses up to the present time, the higher the value. Calculate the value.
Specifically, the usefulness evaluation unit 131 approximates the cumulative number of accesses to the time axis with a function that converges to a certain value on the premise that the access disappears after a sufficient time elapses, and the convergence value is used. The difference in the cumulative number of accesses at time t is used as the usefulness evaluation value.
When the usefulness evaluation unit 131 calculates the usefulness evaluation value for each data (target data), the usefulness evaluation unit 131 transmits the information to the spontaneous movement condition determination device 21.

The access uneven distribution unit 132 calculates the access uneven distribution as indicating the unevenness of the number of accesses to the data from each node adjacent to the node holding a certain data. Hereinafter, a specific description will be given.
FIG. 5 is a diagram for explaining the uneven distribution of access in the present embodiment.
Here, it is assumed that the topology of the storage network is a linear connection of _{nodes N 1} , N ₂ , N ₃ , ..., N _7. As a premise, each node (data management device 1) collects state information of adjacent nodes and links. Further, it is assumed that the data D _{x held by the node N 4} shown in FIG. 5 has been accessed M times in total by the time t. The breakdown is A ⁱ _t times from the user terminal to the node N _i is accommodated ^{_{(Σ 7 i = 1 A i}} t = M). Here, "A ⁱ _t " times is the number of accesses at the node i at time t. However, it is assumed that the state information etc. cannot be acquired after 2 hops at the _{node N 4 , and the data D x} is (A ¹ _t + A ² _t ) times from the node N ₂ and after, and from the node N ₆ and after. (A ⁶ _t + A ⁷ _{t ) times, node N 4} acquires the information that the access has been made.

In the example shown in FIG. 5, for example,
max (Σ ³ _{i = 1} A ⁱ _t , A ⁴ _t , Σ ⁷ _{i = 5} A ⁱ _t ) = Σ ³ _{i = 1} A ⁱ _t
At, the data D _x has more access from the direction of node N _3. Therefore, the access uneven distribution calculation unit 132
Σ ³ _{i = 1} A ⁱ _t / M
Is the access uneven distribution.
When the access uneven distribution calculation unit 132 calculates the access uneven distribution for each data (target data), the access uneven distribution calculation unit 132 transmits the information to the spontaneous movement condition determination device 21.

Returning to FIG. 4, the spontaneous movement condition determination device 21 satisfies a predetermined spontaneous movement condition based on the usefulness evaluation value calculated by the usefulness evaluation unit 131 and the access uneven distribution calculated by the access uneven distribution calculation unit 132. In this case, it is determined that the data is the data that is the target of spontaneous movement (data that is the target of spontaneous movement).

This predetermined spontaneous movement condition is, for example, a condition in which both the usefulness evaluation value and the access uneven distribution are evaluated to be sufficiently high. Specifically, the condition that the usefulness evaluation value is equal to or higher than a predetermined threshold value (predetermined first threshold value) and the access uneven distribution is equal to or higher than a predetermined probability (ratio) (predetermined second threshold value) is satisfied. Satisfaction is a condition for voluntary movement. The predetermined threshold value and the predetermined probability (ratio) are set in advance.
The spontaneous movement condition determination device 21 transmits information to the effect that the data is determined to be the spontaneous movement target data to the spontaneous movement destination selection device 22.

The spontaneous movement destination selection device 22 indicates that another node at a position where the communication cost of the user terminal when accessing the data is reduced is an optimum node indicating a node to be moved from the node holding the spontaneous movement target data (the optimum node). Select as the spontaneous destination node).
This optimum node selection process is executed according to a predetermined procedure shown below.
Here, as shown in FIG. 5, the data D _{x held by the node N 4} will be described as being the data to be spontaneously moved.

(Step 1) from the candidate node (node N ₄ capable of acquiring the state information nodes), than the node that is not in the access ubiquitous high direction. Here, as an example, up to a node two hops ahead will be described as a node (candidate node) in which the node (data management device 1) holding the spontaneous movement target data can acquire the state information. Here, the candidate nodes from the viewpoint of _{node N 4 are nodes N 2} , N ₃ , N ₄ , N ₅ , N ₆ .
Therefore, in (Step 1), for example, when viewed from the node N _4, when high access ubiquitous direction is the node N ₃ side, the node N _5, N ₆ are removed from the candidate node, a node N _2, N ₃ , the candidate node is narrowed down to N _4.
As a result, the candidate node at the position where the communication cost when the user terminal accesses the data increases is excluded. In other words, it is narrowed down to candidate nodes that are in a position where communication costs can be reduced.

(Procedure 2) Select a movable node based on the link usage status to the candidate node.
For example, it is determined that the relative upper limit amount that is set in advance to each link, if the sum of the size of the link usage and data D _x at time t is small, it is possible to use the link to the data movement.
Specifically, among the links shown in FIG. 5 in which the node N ₄ can acquire the state information, _{only the link L 23} is a candidate when the value of the above sum exceeds the upper limit usage amount and does not satisfy the condition. Of the nodes (nodes N ₂ , N ₃ , N ₄ ), the _{nodes N 3} , N _{4 that do not include the link L 23} in the communication path at the time of movement are selected as the movable nodes.

(Procedure 3) Select a retainable node based on the minimum value of the usefulness evaluation value of the data held by the movable node.
For example, the usefulness evaluation value of _{the data D x is S x} , and the minimum value of the usefulness evaluation value of the data held by the nodes N ₃ and N ₄ ^{is S 3} _min and S ⁴ _min (S ³ _min , S ^{4 respectively).} _{When min} <S _{x ), nodes N 3} and N ₄ are selected as the retainable nodes among the movable nodes.
Note that the minimum value at the node (node N ₄₎ efficacy evaluation value S _x data D _x to hold the data D _x, when the minimum value among the data held by the movable nodes, i.e., S _x When = S ⁴ _min <S ³ _min , the spontaneous movement destination selection device 22 transmits information to that effect to the archive instruction device 23. Then, archive indication device 23 transmits the node (node N ₄₎ that hold the data D _x, the indication information to be archived the data D _x, the spontaneous movement processing unit 130 (the archive execution unit 134). Archiving run section 134, the archive to move from the hot storage into a cold storage, to perform its data D _x.

(Procedure 4) _{The sum of the "transfer energy for movement (communication cost)" when the data D x} is moved to the holdable node and held, and the "transfer energy for data acquisition (communication cost)" by the user terminal is Select the smallest optimal node.
For example, as a simple model, the magnitude of transfer energy is calculated as a value proportional to the data size and the number of communication hops. Specifically, in the example shown in FIG. 5, when the data D _{x is moved to the node N 3} which is a node capable of holding the data D x, the transfer energy for the movement is that the number of mobile communication hops is “1” and the data D _When the size of _x is DS x, it becomes C × DS _x × 1 (C is a proportional constant).

Transfer energy data acquisition by the user terminals computes the difference between the case where no moving data D _x (holding data D _x at the node N _4).
[Before node N ₂ ]
From the user terminal accommodated by the node beyond node N _{2 , access of S x} × (A ¹ _t + A ² _t ) / M (times) is expected in the future, and data D _x is moved to _{node N 3.} in order to approach one hop, there is reduction of the _{C × DS x × 1 × (} a 1 t + a 2 t) / M.
[Node N ₃ ]
From the user terminal accommodated by node N _{3 , access of S x} × A ³ _t / M (times) is expected in the future, and by moving data D _{x to node N 3} , one hop approaches, so C × It has the effect of reducing _{DS x} x 1 x A ³ _{t / M.}
[Node N ₄ ]
From the user terminal accommodated by the node N _{4 , S x} × A ⁴ _t / M (times) is expected to be accessed in _{the future, and by moving the data D x to the node N 3} , the data D x is moved away by one hop. It has the effect of increasing _{DS x} × 1 × A ⁴ _{t / M.}
[Node N ₅ ]
_{Access of S x} × A ⁵ _t / M (times) is expected from the user terminal accommodated by node N _5, and moving data D _{x to node N 3} moves the data D x away by one hop, so C × It has the effect of increasing _{DS x} × 1 × A ⁵ _{t / M.}
[Before node N ₆ ]
From the user terminal accommodated by the node beyond node N _{6 , access of S x} × (A ⁶ _t + A ⁷ _t ) / M (times) is expected in the future, and data D _x is moved to _{node N 3.} in order away one hop, there is an increase effect of _{C × DS x × 1 × (} a 6 t + a 7 t) / M.

Incidentally, spontaneous migration destination selection unit 22, in (Step 3), if the node N _3, N ₄ is selected as the holdable node, in (Step 4), the node N _3, N ₄ is subject It becomes.
The spontaneous movement destination selection unit 22, in (Step 4), and transfer energy for moving, the sum of the transfer energy of the data acquisition by the user terminals, each capable of holding node (here, node N _3, N ₄ ) is calculated, and the node with the smallest sum is selected as the optimum node (spontaneous movement destination node).
Further, the spontaneous movement destination selection device 22 is not limited to the case where all of the above (procedure 1) to (procedure 4) are executed, but also when any one or combination of these procedures is executed. good.
Spontaneous migration destination selection unit 22 selects the optimum node (spontaneous destination nodes: for example, the node N ₃₎ transmitting the information, the spontaneous movement processing unit 130 (spontaneous migration execution unit 133).

_{Returning to FIG. 4, the spontaneous movement execution unit 133 selects the data (here, data D x} ) determined by the spontaneous movement condition determination device 21 to be the spontaneous movement target data, and the optimum node selected by the spontaneous movement destination selection device 22. (Spontaneous movement destination node: For example, node N ₃ ) is moved (spontaneous movement).

The archive instruction device 23 transmits instruction information for moving the data having the smallest usefulness evaluation value among the data stored in the hot storage of the own node to the cold storage of the own node to the data management device 1.
Then, as described above, the archive execution unit 134 voluntarily determines that the validity evaluation value of the data to be processed is the minimum value among all the data held by the movable node described above. When the data is determined, the data is archived by receiving the instruction information from the archive instruction device 23 and moving from the hot storage (finite capacity storage unit 100) to the cold storage (infinite capacity storage unit 105).

Returning to FIG. 3, the data storage unit 140 receives data (for example, live data) from a device (Publisher) P that generates (collects) data, another data management device 1, or the like via a network. Then, when the data storage unit 140 receives the data, the data storage unit 140 confirms the capacity of the data. Then, if the data storage unit 140 has a free capacity of its own finite capacity storage unit 100 (hot storage) and can be stored, the data storage unit 140 stores the data in the finite capacity storage unit 100.
On the other hand, when the data storage unit 140 has no free space in its own finite capacity storage unit 100 (hot storage), the data storage unit 140 has a finite capacity storage unit 100 (the finite capacity storage unit 100) of any of the adjacent data management devices 1 capable of acquiring state information. Whether or not there is free space in the hot storage) for storing the data is determined based on, for example, the information acquired by the status monitoring unit 110, and if there is free space, the data is transferred to the data management device 1. do.
Then, if there is no free space in the finite capacity storage unit 100 (hot storage) of all the data management devices 1 from which the state information can be acquired, the data storage unit 140 forces information to that effect (information on the received data). It is transmitted to the movement target data selection device 31.

The data storage unit 140 has its own data management device 1 selected as the optimum node (spontaneous movement destination node) by the above-mentioned spontaneous movement destination selection device 22 of the other data management system 1000, and the spontaneous movement processing unit 130. Data may be received as a result of spontaneous movement by. In this case, the processing of the data storage unit 140 for the spontaneously moved data is performed by the data storage unit 140 because the adjacent data management devices 1 from which the state information can be acquired are different in each of the data management devices 1. Is similarly performed in the data management device 1 after the spontaneous movement.

When the forced movement processing unit 150 receives data (for example, live data) and tries to store it in the storage unit 12, the finite capacity storage unit of all the data management devices 1 (including itself) from which state information can be acquired When there is no free space in 100 (hot storage), the process of forcibly moving or archiving is determined. Regarding this determination, the forced displacement processing unit 150 has a predetermined loss (“archive evaluation value” described later) when the forced displacement target data is archived in its own infinite capacity storage unit 105 (cold storage), and the forced displacement target. The data is compared with the loss when the data is forcibly moved to the forced movement destination node (“forced movement evaluation value” described later).
As the forced movement target data, the forced movement target data selection device 31 selects the data having the smallest usefulness evaluation value among the data stored in the finite capacity storage unit 100 (hot storage) of its own data management device 1. This is the data selected as the data to be forcibly moved. Further, the forced movement destination node is a node in which the forced movement destination selection device 32 selects the node having the minimum usefulness evaluation value (data management device 1) as the forced movement destination node.
Hereinafter, the function of the forced movement processing unit 150 and the details of the device group related to the forced movement will be described with reference to FIG. 6 and the like.

FIG. 6 is a diagram for explaining the function of the forced movement processing unit 150 according to the present embodiment and the details of the device group related to the forced movement.
As shown in FIG. 6, the forced movement processing unit 150 includes an archive evaluation unit 151, a forced movement evaluation unit 152, a processing decision unit 153, an archive execution unit 154, and a forced movement execution unit 155.

Here, it is assumed that there is no free space in the finite capacity storage unit 100 (hot storage) of all the data management devices 1 from which the state information can be acquired at time t. Further, the minimum data of the usefulness evaluation value of the node N _i ^{is defined as the data D i} _min . Then, as shown in FIG. 7 described later, it _{is assumed that the node N 4} has received the new data D _new.

First, when the forced movement target data selection device 31 _{acquires information indicating that new data D new} has been received from the data storage unit 140, it stores it in the finite capacity storage unit 100 (hot storage) of its own data management device 1. Among the data, the data having the smallest usefulness evaluation value (here, data D ⁴ _min ) is selected as the data to be forcibly moved.
The data with the smallest usefulness evaluation value (here, data D ⁴ _min ) is selected as the data to be forcibly moved. The lower the usefulness evaluation value, the smaller the number of future accesses, and the node (data management device). This is because there is little effect even if it is moved from 1).
The forced movement target data selection device 31 has a usefulness evaluation unit 131 (FIG.) in the spontaneous movement processing unit 130 described above for each data stored in the finite capacity storage unit 100 (hot storage) of its own data management device 1. Similar to 4), the usefulness evaluation value is calculated as an evaluation value in which the larger the predicted value of the number of accesses in the future (from the present time to the future), the higher the value.
When the forced movement target data selection device 31 selects the forced movement target data, the forced movement target data selection device 31 transmits the information of the forced movement target data to the forced movement processing unit 150 (archive evaluation unit 151) and the forced movement destination selection device 32.

The archive evaluation unit 151 sets the archive evaluation value when the data to be forcibly moved (here, data D ⁴ _min ) is archived in its own infinite capacity storage unit 105 (cold storage) without being moved to another node. calculate.
This archive evaluation value indicates the total amount of economic loss (predetermined loss) for which data cannot be acquired in real time after archiving. Here, when there is an access to the archived data, it is assumed that an economic loss CP occurs as compensation for not being able to acquire the data in real time.
For example, the archive evaluation unit 151 sets the archive evaluation value as S ⁴ _min × CP when the usefulness evaluation value when archiving the ^{forced movement target data (data D 4} _min ^{) is S 4} _min (FIG. 7). Reference numeral a).

The forced movement destination selection device 32 selects as the forced movement destination node the node that holds the data having the smallest usefulness evaluation value among the movable nodes for the forced movement target data.
The movable node is the same as the description in the spontaneous movement destination selection device 22, and among the nodes (candidate nodes) from which the node can acquire the state information, the link usage amount to the candidate node and the forced movement target data. Based on the size of (data D ⁴ _min ), it is a node excluding the node that uses the link whose data cannot be moved at the upper limit usage of each link.
Here, the node forced movement target data N ₄ (data D ⁴ _min) movable node node N ₃ for, N _4, N _5, and a N _6, usability evaluation value is minimum data (min ( Node N ₅ holding S ⁱ _min | 3 ≦ i ≦ 6) = S ⁵ _min ) is selected as the forced movement destination node.
When the forced movement destination selection device 32 selects the forced movement destination node, the forced movement destination selection device 32 transmits the information of the forced movement destination node to the forced movement processing unit 150 (forced movement evaluation unit 152).

The forced movement evaluation unit 152 calculates the sum of the "data transfer energy (communication cost) due to the forced movement" and the "archive evaluation value of the data archived at the forced movement destination node" as the forced movement evaluation value.
Specifically, the transfer energy generated by the data movement of the forced movement target data (data D ⁴ _min ^{) is TC (= C × DS 4} _min × 1) (reference numeral b in FIG. 7). C is a constant of proportionality.
Further, assuming that the capacity overflow occurs when the node N ₅ receives the data to be forcibly moved (data D ⁴ _min ) and the data D ⁵ _min is archived, the archive evaluation value is S ⁵ _min × CP (FIG. 7). Reference numeral c).
As a result, the forced movement evaluation unit 152 ^{calculates TC + S 5} _min × CP as the forced movement evaluation value.

Returning to FIG. 6, the processing determination unit 153 _{compares the archive evaluation value of the node that has received the new data D new} with the forced movement evaluation value, and selects the smaller one as the processing execution target.
^{For example, if S 4} _min × CP <TC + S ⁵ _min × CP, the processing determination unit 153 determines that the data D ⁴ _min is archived in its own infinite capacity storage unit 105 (cold storage).
On the other hand, if S ⁴ _min × CP> TC + S ⁵ _min × CP, the processing determination unit 153 determines that the data D ⁴ _min is forcibly moved to the forced movement destination node (node N ₅ ).

When the processing decision unit 153 decides to execute the archive, the archive execution unit 154 selects the data (data D ⁴ _min ) having the minimum usefulness evaluation value of the node (node N _{4 ) that has received the new data D new.} , The archive that moves from the finite capacity storage unit 100 (hot storage) to the infinite capacity storage unit 105 (cold storage) is executed.

When the processing decision unit 153 determines that the forced movement is to be performed, the forced movement execution unit 155 is the data for which the usefulness evaluation value of the node (node N _{4 ) that has received the new data D new is the minimum.} Data D ⁴ _min ) is moved (forced move) to the forced move destination node (node N _5).

Returning to FIG. 3, the generation interval adjusting device 40 adjusts the device (Publisher) having a high real-time demand so as to shorten the data generation interval in order to keep the AoI of the latest data of the device small. Further, the generation interval adjusting device 40 adjusts the device having a low real-time requirement so as to lengthen the data generation interval of the device in order to reduce the network load.

Here, the condition monitoring unit 110 of the data management device 1 acquires information on the number of accesses to the data within a predetermined time after the data is generated and stores the information in the storage unit 12. Then, the generation interval adjusting device 40 refers to the information of the number of accesses stored in the storage unit 12, and calculates a value proportional to the number of accesses within a predetermined time as the real-time request degree for each data.
The generation interval adjusting device 40 generates instruction information for lengthening (adjusting) the data generation interval for the device that generates data according to the real-time requirement. Then, the generation interval adjusting device 40 adjusts the data generation interval on a device-by-device basis by transmitting the generated instruction information to the device that generates the data.

In the data generation interval adjustment process by the generation interval adjusting device 40, for example, the data management device 1 stores a certain data in the finite capacity storage unit 100 (hot storage) or the infinite capacity storage unit 105 (cold storage). It may be performed when the acquisition request from the user terminal is received. Further, the generation interval adjusting device 40 sets the data generation interval at a predetermined time interval for the device that generates each data stored in the finite capacity storage unit 100 (hot storage) and the infinite capacity storage unit 105 (cold storage). Adjustments may be made.

<Modified example of the configuration of this embodiment>
In the data management system 1000 according to the present embodiment described above, as shown in FIG. 3, the data management device 1 includes both the spontaneous movement processing unit 130 and the forced movement processing unit 150 in the control unit 10. A group of devices related to spontaneous movement (spontaneous movement condition determination device 21, spontaneous movement destination selection device 22, archive instruction device 23) and a device group related to forced movement (forced movement target data selection device 31, forced movement destination selection device 32). Explained as.
However, the embodiment of the present invention is not limited to the data management system 1000 shown in FIG. For example, as shown in the data management system 1000A of FIG. 8, the configuration may not include the functions related to the forced movement (forced movement processing unit 150 and the device group related to the forced movement) shown in FIG. The data management device 1A of the data management system 1000A includes a finite capacity storage unit 100 (hot storage), an infinite capacity storage unit 105 (cold storage), a spontaneous movement processing unit 130, a group of devices related to spontaneous movement, and the like. Even when the storage capacity of the finite capacity storage unit 100 (hot storage) is insufficient, the data can be stored without being deleted. Further, the spontaneous movement processing unit 130 can move the data (spontaneous movement target data) that satisfies a predetermined spontaneous movement condition based on the usefulness evaluation value and the access uneven distribution to the optimum node. Therefore, useful data that is highly likely to be accessed from the user terminal can be stored in the finite capacity storage unit 100 (hot storage) of the optimum node (data management device 1A) having less transfer energy.

Further, as shown in the data management system 1000B of FIG. 9, the configuration may not include the functions related to the spontaneous movement shown in FIG. 3 (the spontaneous movement processing unit 130 and the device group related to the spontaneous movement). The data management device 1B of the data management system 1000B is newly provided with a finite capacity storage unit 100 (hot storage), an infinite capacity storage unit 105 (cold storage), a forced movement processing unit 150, a group of devices related to forced movement, and the like. When trying to store data, even if the storage capacity of its own finite capacity storage unit 100 (hot storage) is insufficient, the data can be stored without being deleted. Further, even if the forced movement processing unit 150 has no free space in the finite capacity storage unit 100 (hot storage) of each data management device 1B, the forced movement processing unit 150 can be used in the finite capacity storage unit 100 (hot storage) of the data management device 1B. Of the stored data, the data with the smallest usefulness evaluation value (data to be forcibly moved) is forcibly moved to another data management device 1B, and new data is transferred to its own finite capacity storage unit 100 (hot storage). Can be remembered.

Further, the data management systems 1000 (FIG. 3), 1000A (FIG. 8), and 1000B (FIG. 9) according to the present embodiment may be configured not to include the generation interval adjusting device 40.

<Processing of data management device>
Next, the processing executed by the data management system 1000 (see FIG. 3) will be described. Here, each processing content related to spontaneous movement, forced movement, and generation interval adjustment will be specifically described.
The same processing is performed in the data management system 1000A shown in FIG. 8 and the data management system 1000B shown in FIG.

≪Data arrangement control by spontaneous movement≫
First, data arrangement control by spontaneous movement of the data management system 1000 will be described.
Here, the status monitoring unit 110 (FIG. 3) of the data management device 1 determines the access source for each data and the number of processes (access count) for each data from another adjacent data management device 1 capable of acquiring the status information. It is assumed that information and status information such as the usage amount of each link have been acquired in advance.
Further, in the spontaneous movement processing unit 130 (and the device group related to the spontaneous movement), for example, the acquisition request processing unit 120 receives a data acquisition request (request), and the finite capacity storage unit 100 (hot storage) in the storage unit 12 is used. ) May be triggered by the transmission of the data stored in), and the data arrangement control by the spontaneous movement shown below may be executed for the data. Further, the spontaneous movement processing unit 130 executes the following data arrangement processing by spontaneous movement for each data stored in the finite capacity storage unit 100 (hot storage) in the storage unit 12 at predetermined time intervals. You may. At that time, the spontaneous movement processing unit 130 may execute the data arrangement processing by the spontaneous movement in order from, for example, the data having the largest number of accesses.

FIG. 10 is a flowchart showing a flow of data arrangement control by spontaneous movement of the data management system 1000 according to the present embodiment.
First, the usefulness evaluation unit 131 (see FIG. 4) of the data management device 1 (spontaneous movement processing unit 130) calculates a usefulness evaluation value based on the prediction of the future access number of the target data (target data). (Step S10).
Then, the usefulness evaluation unit 131 transmits the calculated usefulness evaluation value to the spontaneous movement condition determination device 21.

Next, the access uneven distribution calculation unit 132 of the spontaneous movement processing unit 130 calculates the access uneven distribution indicating the bias regarding the adjacent node of the access source (step S11).
The access uneven distribution calculation unit 132 transmits the calculated access uneven distribution information to the spontaneous movement condition determination device 21.

Subsequently, the spontaneous movement condition determination device 21 determines whether or not the target data satisfies the predetermined spontaneous movement conditions regarding the usefulness evaluation value and the access uneven distribution (step S12).
The predetermined spontaneous movement condition is, for example, that the usefulness evaluation value is equal to or higher than a predetermined threshold value (predetermined first threshold value) and the access uneven distribution is equal to or higher than a predetermined probability (predetermined second threshold value). It is a condition.
Here, if the predetermined spontaneous movement condition is not satisfied (step S12 → No), the process ends. On the other hand, when a predetermined spontaneous movement condition is satisfied (step S12 → Yes), the spontaneous movement condition determination device 21 considers the data to be data to be spontaneously moved (spontaneous movement target data) and spontaneously moves. The information is transmitted to the preselection device 22, and the process proceeds to the next step S13.

In step S13, the spontaneous movement destination selection device 22 selects the optimum node (spontaneous movement destination node) as the movement destination of the spontaneous movement target data. Details of this optimum node selection process will be described later (see FIG. 11). Then, the spontaneous movement destination selection device 22 transmits the information of the selected optimum node (spontaneous movement destination node) to the spontaneous movement processing unit 130 (spontaneous movement execution unit 133).

Next, the spontaneous movement execution unit 135 executes a process of moving (spontaneous movement) the data to be spontaneously moved to the data management device 1 which is the optimum node (spontaneous movement destination node) selected in step S13 (step S14). ..

By doing so, the data management device 1 (spontaneous movement processing unit 130) of the data management system 1000 can obtain data (spontaneous movement target data) that satisfies a predetermined spontaneous movement condition based on the usefulness evaluation value and access uneven distribution. , Can be moved to the optimal node. Therefore, useful data that is highly likely to be accessed from the user terminal can be stored in the finite capacity storage unit 100 (hot storage) of the optimum node (data management device 1) having less transfer energy.

[Optimal node selection process]
FIG. 11 is a flowchart showing the flow of the optimum node selection process of the data management system 1000 according to the present embodiment.
This optimum node selection process is a process executed by the spontaneous movement destination selection device 22 in step S13 in the data arrangement control by spontaneous movement shown in FIG.

First, the spontaneous movement destination selection device 22 (FIG. 3) identifies a node (candidate node) from which the state information can be acquired in the node (data management device 1 connected to itself) that stores the spontaneous movement target data. Then, the spontaneous movement destination selection device 22 excludes the nodes other than the direction in which the access uneven distribution is high (step S131: procedure 1).

Next, the spontaneous movement destination selection device 22 selects a movable node based on the link usage status up to the candidate node (step S132: procedure 2).

Subsequently, the spontaneous movement destination selection device 22 confirms the minimum value of the usefulness evaluation value of the data held by each of the movable nodes with reference to the storage unit 12 of the data management device 1. Then, when the confirmed usefulness evaluation value is smaller than the usefulness evaluation value of the spontaneous movement target data, the spontaneous movement destination selection device 22 provides a movable node that holds the confirmed usefulness evaluation value data. , Select as a retainable node (step S133: step 3).

Then, the spontaneous movement destination selection device 22 moves and holds the spontaneous movement target data to the holdable node, and the "transfer energy (communication cost) for movement" and the "transfer energy for data acquisition" by the user terminal. The node having the smallest sum with "(communication cost)" is selected as the optimum node from the holdable nodes (step S134: step 4).
In this way, the spontaneous movement destination selection device 22 can select the optimum node for the spontaneous movement target data.

≪Data placement control by forced displacement≫
Next, data arrangement control by forced movement of the data management system 1000 will be described.
Here, the status monitoring unit 110 (FIG. 3) of the data management device 1 is using the link between each data management device 1 from another adjacent data management device 1 capable of acquiring the status information (link use). Amount), it is assumed that information (state information) such as free capacity of the finite capacity storage unit 100 (hot storage) of each data management device 1 and data having the minimum usefulness evaluation value is acquired.
Further, it is assumed that there is no free space in the finite capacity storage unit (hot storage) of all the data management devices 1 capable of acquiring the state information.
The forced movement processing unit 150 and the device group related to the forced movement start processing when the data storage unit 140 receives new data.

FIG. 12 is a flowchart showing a flow of data arrangement control by forced movement of the data management system 1000 according to the present embodiment.
First, when the data storage unit 140 of the data management device 1 receives new data, the data storage unit 140 confirms the capacity of the data. Then, the data storage unit 140 determines whether or not the finite capacity storage unit 100 (hot storage) has enough free space to store new data (step S20).
Then, if there is free space (step S20 → Yes), the data storage unit 140 stores the new data in the finite capacity storage unit 100 (hot storage) (step S21). On the other hand, if there is no free space (step S20 → No), the data storage unit 140 transmits the new data information to the forced movement target data selection device 31, and proceeds to the next step S22.

In step S22, the forced movement target data selection device 31 calculates a usefulness evaluation value for each data stored in the finite capacity storage unit 100 (hot storage) of the data management device 1 connected to itself, and evaluates the usefulness. The data with the smallest value is selected as the data to be forcibly moved.
When the forced movement target data selection device 31 selects the forced movement target data, the forced movement target data selection device 31 transmits the information of the forced movement target data to the forced movement processing unit 150 (archive evaluation unit 151) and the forced movement destination selection device 32.

Next, the archive evaluation unit 151 calculates an archive evaluation value when the forced movement target data is archived in its own infinite capacity storage unit 105 (cold storage) (step S23).

Subsequently, the forced movement destination selection device 32 selects the node holding the data having the minimum usefulness evaluation value among the movable nodes for the forced movement target data as the forced movement destination node (step S24).
The forced movement destination selection device 32 transmits the information of the selected forced movement destination node to the forced movement processing unit 150 (forced movement evaluation unit 152).

Then, the forced movement evaluation unit 152 determines the "data transfer energy (communication cost) due to forced movement" when the forced movement target data is moved to the forced movement destination node, and the usefulness evaluation value stored in the forced movement destination node. The sum of the archive evaluation value when the minimum data is archived (“the archive evaluation value of the data archived at the forced movement destination node”) is calculated as the forced movement evaluation value (step S25).

Next, the processing determination unit 153 compares the archive evaluation value of the node that received the new data calculated in step S23 with the forced displacement evaluation value calculated in step S25, and sets the smaller one as the processing execution target. Determine (step S26).
Here, the processing determination unit 153 determines that the archive processing is executed if the archive evaluation value of the node that has received the new data is smaller than the forced movement evaluation value. On the other hand, the processing determination unit 153 determines that the forced movement is executed if the forced movement evaluation value is smaller than the archive evaluation value of the node that has received the new data.
If the archive evaluation value of the node that has received the new data and the forced movement evaluation value are the same, the process determination unit 153 may execute the predetermined process or randomly. Either process may be determined.

Next, when the process determination unit 153 determines in step S26 to execute the archive process, the archive execution unit 154 determines the data having the minimum usefulness evaluation value of the node that has received the new data (forced movement target data). Is transferred from the finite capacity storage unit 100 (hot storage) to the infinite capacity storage unit 105 (cold storage) (step S27). Then, the process returns to step S20.

On the other hand, when the processing determination unit 153 determines in step S26 to execute the forced movement, the forced movement execution unit 155 is the data having the minimum usefulness evaluation value of the node that has received the new data (forced movement target data). Is moved (forced movement) to the forced movement destination node (step S28). Then, the process returns to step S20.

By doing so, the data management device 1 (forced movement processing unit 150) of the data management system 1000 can be used even when the finite capacity storage unit 100 (hot storage) of each data management device 1 has no free space. , Of the data stored in the finite capacity storage unit 100 (hot storage) of each data management device 1, the data having the smallest usefulness evaluation value (forced movement target data) is forcibly moved to another data management device 1. , New data can be stored in its own finite capacity storage unit 100 (hot storage).

≪Adjustment of data generation interval according to real-time request≫
Next, the data generation interval adjustment according to the real-time request by the generation interval adjusting device 40 (FIG. 3) of the data management system 1000 will be described.
Here, it is assumed that the storage unit 12 stores information on the number of accesses to each data via the state monitoring unit 110.

FIG. 13 is a flowchart showing a flow of adjusting the data generation interval of the data management system 1000 according to the present embodiment.
First, the acquisition request processing unit 120 of the data management device 1 receives and stores a data acquisition request (request) from the user terminal (not shown) or another data management device 1 housed in the data management device 1. The data stored in the finite capacity storage unit 100 (hot storage) or the infinite capacity storage unit 105 (cold storage) in the unit 12 is returned as response information (step S30).

Next, the generation interval adjusting device 40 calculates a value proportional to the number of accesses within a predetermined time as a real-time request degree for the data for which the acquisition request has been received (step S31).
The generation interval adjusting device 40 may monitor the acquisition request processing unit 120 of the data management device 1 to obtain information on the data for which the acquisition request has been received, or the acquisition request processing unit 120 has returned the data. Information about the data may be acquired by setting the information to be transmitted to the generation interval adjusting device 40.
Subsequently, the generation interval adjusting device 40 generates instruction information for adjusting the data generation interval to be shorter as the real-time requirement is higher, and transmits the data to the generating device (Publisher) (step S32).

By doing so, the generation interval adjusting device 40 of the data management system 1000 can adjust the latest data of the device having a high real-time requirement so that the AoI is smaller, that is, the data generation interval is shortened. On the other hand, the generation interval adjusting device 40 can adjust the latest data of the device having a low real-time requirement so that the AoI is larger, that is, the data generation interval is lengthened. Therefore, it is possible to reduce the network load for moving the data.

<Hardware configuration>
Data management device 1 (1A, 1B) and each device (spontaneous movement condition determination device 21, spontaneous movement destination selection device 22, archive instruction device 23, forced movement target data selection device 31, forced movement destination selection device) according to the present embodiment. 32. The generation interval adjusting device 40) is realized by, for example, a computer 900 having a configuration as shown in FIG.
FIG. 14 is a hardware configuration diagram showing an example of the data management devices 1 (1A, 1B) according to the present embodiment and the computer 900 that realizes the functions of each device. The computer 900 includes a CPU (Central Processing Unit) 901, a ROM (Read Only Memory) 902, a RAM 903, an HDD (Hard Disk Drive) 904, an input / output I / F (Interface) 905, a communication I / F 906, and a media I / F 907. Have.

The CPU 901 operates based on a program stored in the ROM 902 or the HDD 904, and is controlled by the control unit 10 (FIGS. 3, 8, 9, 9, etc.). The ROM 902 stores a boot program executed by the CPU 901 when the computer 900 is started, a program related to the hardware of the computer 900, and the like.

The CPU 901 controls an input device 910 such as a mouse and a keyboard and an output device 911 such as a display and a printer via the input / output I / F 905. The CPU 901 acquires data from the input device 910 and outputs the generated data to the output device 911 via the input / output I / F 905. A GPU (Graphics Processing Unit) or the like may be used together with the CPU 901 as the processor.

The HDD 904 stores a program executed by the CPU 901, data used by the program, and the like. The communication I / F906 receives data from another device via a communication network (for example, NW (Network) 920) and outputs the data to the CPU 901, and the data generated by the CPU 901 is transmitted to another device via the communication network. Send to the device.

The media I / F907 (data read / write module) reads the program or data stored in the recording medium 912 and outputs the program or data to the CPU 901 via the RAM 903. The CPU 901 loads the program related to the target processing from the recording medium 912 onto the RAM 903 via the media I / F 907, and executes the loaded program. The recording medium 912 is an optical recording medium such as a DVD (Digital Versatile Disc) or PD (Phase change rewritable Disk), a magneto-optical recording medium such as an MO (Magneto Optical disk), a magnetic recording medium, a semiconductor memory, or the like.

For example, when the computer 900 functions as the data management device 1 (1A, 1B) of the present invention or each of the above devices, the CPU 901 of the computer 900 executes the program loaded on the RAM 903 to execute the data management device 1 (1A, 1B). 1A, 1B) and the functions of each device are realized. Further, the data in the RAM 903 is stored in the HDD 904. The CPU 901 reads a program related to the target process from the recording medium 912 and executes it. In addition, the CPU 901 may read a program related to the target processing from another device via the communication network (NW920).

<Effect>
Hereinafter, the effects of the data management system 1000 (1000A) and the like according to the present invention will be described.
The data management system according to the present invention is a data management system 1000 (1000A) including a data management device 1 (1A) which is a node in a storage network composed of a plurality of nodes functioning as storage devices, and data management. The system 1000 includes a data management device 1 having hot storage and cold storage for storing data, a spontaneous movement condition determination device 21 and a spontaneous movement destination selection device 22 connected with the data management device 1 as its own node. When the data stored in the hot storage satisfies a predetermined spontaneous movement condition regarding access to the data, the spontaneous movement condition determination device 21 includes the archive instruction device 23, and the spontaneous movement target data. The spontaneous movement destination selection device 22 moves the other nodes other than the own node, which are in a position where the communication cost of the user terminal when accessing the data is reduced, from the node holding the spontaneous movement target data. Selected as the spontaneous movement destination node indicating the destination node, the archive instruction device 23 shows a usefulness evaluation value showing a higher value as the prediction of the number of future accesses is larger among the data stored in the hot storage of the own node. Sends instruction information to move the minimum data to the cold storage of its own node to the data management device 1, and when the data management device 1 moves the spontaneous movement target data to the spontaneous movement destination node and receives the instruction information. The feature is that the data with the minimum usefulness evaluation value stored in the hot storage of the own node is moved to the cold storage of the own node.

As described above, the data management system 1000 (1000A) is provided with the cold storage together with the hot storage in the storage unit 12 of the data management device 1 (1A), so that the cold storage can be used when there is no free space in the hot storage. Data can be moved and stored.
Further, the spontaneous movement condition determination device 21 selects data that satisfies a predetermined spontaneous movement condition regarding access as the spontaneous movement target data. The spontaneous movement destination selection device 22 selects a spontaneous movement destination node at a position where the communication cost of the user terminal is reduced. Then, the data management device 1 can move the spontaneous movement target data to the spontaneous movement destination node.
Therefore, useful data that is likely to be accessed from the user terminal can be moved to a node that has a low communication cost from the user terminal.
Further, the data management device 1 can receive the instruction information from the archive instruction device 23 and move the data having the minimum usefulness evaluation value stored in the hot storage of the own node to the cold storage of the own node. Therefore, according to the data management system 1000 (1000A), even when the storage capacity of the storage device is insufficient, the data can be stored without being deleted.

Further, in the data management system 1000 (1000A), a value proportional to the number of accesses of the data stored in the hot storage within a predetermined time is calculated as a real-time requirement, and the higher the real-time requirement, the shorter the data generation interval is adjusted. The device for generating the instruction information to be generated and generating the data is further provided with a generation interval adjusting device 40 for outputting the instruction information.

By doing so, the generation interval adjusting device 40 of the data management system 1000 (1000A) can reduce AoI by shortening the data generation interval of the device having a high real-time demand. Further, the generation interval adjusting device 40 can reduce the network load when moving the data by lengthening the data generation interval of the device having a low real-time requirement.

Further, the data management device is a data management device 1 (1A) of a data management system 1000 (1000A) including a data management device 1 (1A) which is a node in a storage network composed of a plurality of nodes functioning as storage devices. The data management system 1000 includes a data management device 1, a spontaneous movement condition determination device 21, a spontaneous movement destination selection device 22, and an archive instruction device 23, which are connected with the data management device 1 as its own node. The data management device 1 has a hot storage and a cold storage for storing data, and when the data stored in the hot storage satisfies a predetermined spontaneous movement condition regarding access to the data, a spontaneous movement condition is satisfied. The spontaneous movement target data, which is the data determined by the determination device 21, is in a position where the communication cost of the user terminal when accessing the data is reduced, and is used as a destination node from the node holding the spontaneous movement target data. Of the data stored in the hot storage of the own node after moving to the spontaneous move destination node, which is a node other than the own node, selected by the spontaneous move destination selection device 22, the larger the prediction of the future access number, the higher the value. Receives instruction information from the archive instruction device 23 to move the data with the smallest usefulness evaluation value indicating the value to the cold storage of the own node, and the data with the smallest usefulness evaluation value stored in the hot storage of the own node, own It is characterized by moving it to the cold storage of the node.

In this way, the data management device 1 (1A) can move the spontaneous movement target data determined by the spontaneous movement condition determination device 21 to the spontaneous movement destination node selected by the spontaneous movement destination selection device 22. Therefore, useful data that is likely to be accessed from the user terminal can be moved to a node that has a low communication cost from the user terminal.
Further, the data management device 1 can receive the instruction information from the archive instruction device 23 and move the data having the minimum usefulness evaluation value stored in the hot storage of the own node to the cold storage of the own node. Therefore, the data management device 1 (1A) can store the data without deleting it even when the storage capacity of the storage device is insufficient.

Further, the spontaneous movement condition determination device is a spontaneous movement condition determination device of the data management system 1000 (1000A) including the data management device 1 (1A) which is a node in a storage network composed of a plurality of nodes functioning as storage devices. The data management system 1000 includes a data management device 1 having hot storage and cold storage for storing data and a spontaneous movement condition determination device 21, and the spontaneous movement condition determination device 21 is a hot storage. When the data stored in the data satisfies a predetermined spontaneous movement condition regarding access to the data, the data is determined to be the spontaneous movement target data.

In this way, the spontaneous movement condition determination device 21 can determine that the data satisfying the predetermined spontaneous movement condition regarding access is the spontaneous movement target data indicating the data to be the target of the spontaneous movement.
The predetermined spontaneous movement condition regarding the access determined by the spontaneous movement condition determination device 21 determines, for example, the data as the spontaneous movement target data when both the usefulness evaluation value and the access uneven distribution are higher than the predetermined threshold value. That is. According to such a predetermined spontaneous movement condition regarding access, when there is a high possibility that the data will be accessed in the future and the probability that the node holding the data is a demand point node indicating a node that accepts an acquisition request is low. Since it is determined to be the data to be spontaneously moved, it is possible to select and move the data having a high effect of reducing the communication cost of the user terminal.

Further, the spontaneous movement destination selection device is a spontaneous movement destination selection device of the data management system 1000 (1000A) including the data management device 1 (1A) which is a node in a storage network composed of a plurality of nodes functioning as storage devices. 22; the data management system 1000 is a data management device 1 having hot storage and cold storage for storing data, and a spontaneous movement condition determination device 21 connected with the data management device 1 as its own node. And the spontaneous movement destination selection device 22 is provided, and the spontaneous movement destination selection device 22 is subjected to the spontaneous movement condition determination device 21 when a predetermined spontaneous movement condition regarding access to the data is satisfied in the data stored in the hot storage. Regarding the spontaneous movement target data that is the determined data, the other nodes other than the own node, which are in a position where the communication cost of the user terminal when accessing the data is reduced, are from the node that holds the spontaneous movement target data. It is characterized in that it is selected as a spontaneous movement destination node indicating a movement destination node.

In this way, the spontaneous movement destination selection device 22 can select another node at a position where the communication cost of the user terminal is reduced as the spontaneous movement destination node. Therefore, the spontaneous movement destination selection device 22 can reduce the communication cost from the user terminal when the spontaneous movement target data is moved.

Further, the archive instruction device is an archive instruction device 23 of the data management system 1000 (1000A) including the data management device 1 (1A) which is a node in a storage network composed of a plurality of nodes functioning as storage devices. The data management system 1000 includes a data management device 1 and an archive instruction device 23 having hot storage and cold storage for storing data, and the archive instruction device 23 is stored in the hot storage of the data management device 1. Of the data, the data with the smallest usefulness evaluation value, which indicates a higher value as the prediction of the number of future accesses is larger, is transmitted to the data management device 1 with instruction information for moving the data to the cold storage of the data management device 1. It is characterized by that.

In this way, the archive instruction device 23 can move the data having the minimum usefulness evaluation value stored in the hot storage to the cold storage by transmitting the instruction information to the data management device 1. Therefore, the archive instruction device 23 can move data that is unlikely to be accessed from the user terminal in the future, that is, data that is less useful, to the cold storage.

The present invention is not limited to the embodiments described above, and many modifications can be made by a person having ordinary knowledge in the art within the technical idea of the present invention.
For example, as shown in the data management device 1C of FIG. 15, a group of devices related to spontaneous movement in the data management system 1000 shown in FIG. 3 (spontaneous movement condition determination device 21, spontaneous movement destination selection device 22, archive instruction device 23). , Each function of the device group related to forced movement (forced movement target data selection device 31, forced movement destination selection device 32) and the generation interval adjustment device 40 is incorporated as a data management device 1C, and can be used as a device in one housing. good. In this case, each function of the spontaneous movement condition determination device 21, the spontaneous movement destination selection device 22, and the archive instruction device 23 is incorporated as the spontaneous movement processing unit 130C. Each function of the forced movement target data selection device 31 and the forced movement destination selection device 32 is incorporated as the forced movement processing unit 150C. Further, the function of the generation interval adjusting device 40 is incorporated in the control unit 10 as the generation interval adjusting unit 160.
Even in this way, the same effects as those of the data management system 1000 according to the present embodiment can be obtained. Further, the data management device 1C shown in FIG. 15 may be configured not to include any of the spontaneous movement processing unit 130C, the forced movement processing unit 150C, and the generation interval adjusting unit 160.

1,1A, 1B Data management device 10 Control unit 11 Input / output unit 12 Storage unit (storage means)
21 Spontaneous movement condition judgment device 22 Spontaneous movement destination selection device 23 Archive instruction device 31 Forced movement target data selection device 32 Forced movement destination selection device 40 Generation interval adjustment device 100 Limited capacity storage unit (hot storage)
105 Infinite capacity storage unit (cold storage)
110 Condition monitoring unit 120 Acquisition request processing unit 130 Spontaneous movement processing unit 131 Usefulness evaluation unit 132 Access uneven distribution calculation unit 133 Spontaneous movement execution unit 134 Archive execution unit 140 Data storage unit 150 Forced movement processing unit 151 Archive evaluation unit 152 Forced movement Evaluation unit 153 Processing decision unit 154 Archive execution unit 155 Forced displacement execution unit 1000, 1000A, 1000B Data management system

Claims (11)

A data management system including a data management device that is the node in a storage network composed of a plurality of nodes that function as storage devices.
The data management system includes the data management device having hot storage and cold storage for storing data, a spontaneous movement condition determination device, a spontaneous movement destination selection device, and a spontaneous movement destination selection device connected by using the data management device as its own node. Equipped with an archive instruction device
When the data stored in the hot storage satisfies a predetermined spontaneous movement condition regarding access to the data, the spontaneous movement condition determination device determines the data as the spontaneous movement target data.
The spontaneous movement destination selection device sets a node other than the own node at a position where the communication cost of the user terminal when accessing the data is reduced as a movement destination from the node holding the spontaneous movement target data. Select as the spontaneous destination node that indicates the node that becomes
Among the data stored in the hot storage of the own node, the archive instruction device moves the data having the smallest usefulness evaluation value, which shows a higher value as the prediction of the number of future accesses is larger, to the cold storage of the own node. The instruction information is transmitted to the data management device, and the instruction information is transmitted.
The data management device is
The voluntary movement target data is moved to the spontaneous movement destination node, and the data is moved to the spontaneous movement destination node.
A data management system characterized in that when the instruction information is received, the data having the minimum usefulness evaluation value stored in the hot storage of the own node is moved to the cold storage of the own node. A value proportional to the number of accesses of the data stored in the hot storage within a predetermined time is calculated as a real-time requirement, and the higher the real-time requirement, the shorter the data generation interval is to generate instruction information, and the data is The data management system according to claim 1, further comprising a generation interval adjusting device for outputting the instruction information in the device for generating the data. A data management device of a data management system including a data management device that is the node in a storage network composed of a plurality of nodes that function as storage devices.
The data management system includes the data management device, a spontaneous movement condition determination device, a spontaneous movement destination selection device, and an archive instruction device connected by using the data management device as a local node.
The data management device is
Has hot storage and cold storage to store data,
When accessing the data stored in the hot storage, the data to be spontaneously moved, which is the data determined by the spontaneous movement condition determination device when the predetermined spontaneous movement condition for accessing the data is satisfied. It is in a position where the communication cost of the user terminal is reduced, and is a node other than the own node, which is selected by the spontaneous movement destination selection device as the destination node from the node holding the spontaneous movement target data. Go to the destination node and
Of the data stored in the hot storage of the own node, the data with the smallest usefulness evaluation value, which shows a higher value as the prediction of the number of future accesses is larger, is the archive instruction for moving the instruction information to move to the cold storage of the own node. A data management device characterized in that the data received from the device and stored in the hot storage of the own node and stored in the hot storage of the own node is moved to the cold storage of the own node. A device for determining spontaneous movement conditions of a data management system including a data management device that is the node in a storage network composed of a plurality of nodes that function as storage devices.
The data management system includes the data management device and the spontaneous movement condition determination device having hot storage and cold storage for storing data.
The spontaneous movement condition determination device is
A spontaneous movement condition determination device, characterized in that, when the data stored in the hot storage satisfies a predetermined spontaneous movement condition regarding access to the data, the data is determined to be spontaneous movement target data. A voluntary movement destination selection device for a data management system including a data management device that is the node in a storage network composed of a plurality of nodes that function as storage devices.
The data management system includes the data management device having hot storage and cold storage for storing data, and a spontaneous movement condition determination device and a spontaneous movement destination selection device connected with the data management device as its own node. I have
The spontaneous movement destination selection device is
When accessing the data stored in the hot storage, the data to be spontaneously moved, which is the data determined by the spontaneous movement condition determination device when the predetermined spontaneous movement condition for accessing the data is satisfied. The feature is that a node other than the own node, which is in a position where the communication cost of the user terminal is reduced, is selected as the spontaneous movement destination node indicating the node to be moved from the node holding the spontaneous movement target data. Spontaneous movement destination selection device. An archive instruction device for a data management system including a data management device that is the node in a storage network composed of a plurality of nodes that function as storage devices.
The data management system includes the data management device and the archive instruction device having hot storage and cold storage for storing data.
The archive instruction device is
Of the data stored in the hot storage of the data management device, the instruction information for moving the data having the smallest usefulness evaluation value, which indicates a higher value as the prediction of the number of future accesses is larger, to the cold storage of the data management device. Is transmitted to the data management device. A data management method for a data management system including a data management device that is the node in a storage network composed of a plurality of nodes that function as storage devices.
The data management system includes the data management device having hot storage and cold storage for storing data, a spontaneous movement condition determination device, a spontaneous movement destination selection device, and a spontaneous movement destination selection device connected by using the data management device as its own node. Equipped with an archive instruction device
When the data stored in the hot storage satisfies a predetermined spontaneous movement condition regarding access to the data, the spontaneous movement condition determination device determines the data as the spontaneous movement target data.
The spontaneous movement destination selection device sets a node other than the own node at a position where the communication cost of the user terminal when accessing the data is reduced as a movement destination from the node holding the spontaneous movement target data. Select as the spontaneous destination node that indicates the node that becomes
Among the data stored in the hot storage of the own node, the archive instruction device moves the data having the smallest usefulness evaluation value, which shows a higher value as the prediction of the number of future accesses is larger, to the cold storage of the own node. The instruction information is transmitted to the data management device, and the instruction information is transmitted.
The data management device is
The voluntary movement target data is moved to the spontaneous movement destination node, and the data is moved to the spontaneous movement destination node.
A data management method characterized in that when the instruction information is received, the data having the minimum usefulness evaluation value stored in the hot storage of the own node is moved to the cold storage of the own node. A program for causing a computer to function as the data management device according to claim 3. A program for causing a computer to function as the spontaneous movement condition determination device according to claim 4. A program for causing a computer to function as the spontaneous movement destination selection device according to claim 5. A program for operating a computer as the archive instruction device according to claim 6.

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