JP2004054845A - Data management device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data management device capable of realizing high speed processing and improving utilization efficiency of a cache by reducing communication traffic between processors. <P>SOLUTION: The data management device is characterized by that it is provided with a plurality of processors carrying out a writing process and reading process of data in response to a request from the outside, one or more external storages storing data, and at least a shared cache device shared by the plurality of processors to temporarily store data to be read or written in regard to the external storages. By such a configuration, cache data is centralized since the plurality of processors share the cache. Consequently, since the communication traffic between the processors can be reduced, processing speed is improved and the utilization efficiency of the cache device is enhanced. Furthermore, the number of times of data transfer between the external storages and the cache device can be reduced also. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a data management device, and more particularly, to a data management device configured as a cluster system.
[0002]
[Prior art]
As an apparatus for storing various data in an external storage device such as a hard disk and providing various services to a client using the data, a data management device such as a file server or a database server is often used. In recent years, in order to provide services to a larger number of clients, this data management apparatus has a cluster (in which a plurality of independently operating processors (generally, computers) are connected in parallel by a high-speed line. clustering) is used. By configuring the data management device as such a cluster system, the reliability of the entire system can be improved and the load on the processor can be distributed. Hereinafter, a configuration example of a general cluster system applied to the data management device will be described with reference to FIGS.
[0003]
In the configuration example shown in FIG. 12, a plurality of (for example, two) processors P1 'and P2' are occupied by exclusive use cache devices (for example, disk caches) SC1 'and SC2' in which data of the same content is stored. External storage devices ES1 ′ and ES2 ′. Each processor P1 ', P2' caches a partial copy of the data stored in the corresponding external storage device ES1 ', ES2' in its own cache device SC1 ', SC2'. , Handles requests from many client terminals.
[0004]
However, in such a system configuration, when data is updated, a large amount of data is exchanged between processors in order to match data in all external storage devices and to match storage contents of all cache devices. There was a problem that communication had to be performed. Therefore, such a system configuration is not suitable for applications in which data is frequently updated. In addition, since all the external storage devices store the same data, not only is the use efficiency of the external storage device inferior, but also the use efficiency of the cache device is reduced because each processor caches a copy of the same data. There was a problem of bad.
[0005]
In the configuration example shown in FIG. 13, the processors P1 'and P2' occupy the cache devices SC1 'and SC2', respectively, and share one external storage device ES '. Each of the processors P1 'and P2' caches a partial copy of the data stored in the shared external storage device ES 'in its own cache device SC1' or SC2 '. Handles requests from many client terminals.
[0006]
However, even in such a system configuration, when data is updated, there is a problem that a large amount of communication must be performed between processors in order to make the storage contents of all cache devices coincide. In addition, since all processors cache the same data in the cache device occupied by themselves, there still remains a problem that the use efficiency of the cache device is poor. Further, since a plurality of cache devices are independently provided for each processor, the same data transfer occurs many times between each cache device and one external storage device, so that the load on the external storage device increases. There was also a disadvantage that it would be lost. In addition, since a plurality of expensive large-capacity cache devices must be provided, there is a problem that the total cost of the devices increases.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above problems, and an object of the present invention is to reduce the amount of communication between a plurality of processors to enable high-speed processing, and to improve the efficiency of use of a cache device. An object of the present invention is to provide a new and improved data management device capable of reducing costs.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, according to a first aspect of the present invention, there are provided a plurality of processors for performing a data write process and a data read process in response to an external request; A data management device is provided, comprising: an external storage device; and a shared cache device that is shared by a plurality of processors and temporarily stores at least data read and written to the external storage device.
[0009]
With this configuration, the processor can write and store data in the external storage device, and can read data stored in the external storage device. Further, the processor can cache data read from the external storage device or data to be written to the external storage device in the shared cache device. As a result, the processor can read out the data cached in the shared cache device at a high speed and provide the read-out data to the outside, and can write the data requested to be written from the outside to the shared cache device at a high speed.
[0010]
Further, according to the above configuration, since a plurality of processors share the shared cache device, data cached on the shared cache device by one processor can be read or rewritten by another processor. In this way, all data cached in the data management device can be unified in the shared cache device. Therefore, when updating data, there is no need to maintain consistency of cache contents among a plurality of cache devices as in the related art, so that there is no need to transfer data between processors. Also, since multiple copies of the same data are not cached, the use efficiency of the cache device is improved. Furthermore, the number of data transfers between the external storage device and the cache device can be reduced.
[0011]
Further, if the shared cache device is configured so that it can be accessed simultaneously by a plurality of processors, a plurality of processors can operate at the same time when a plurality of external requests are made. Is improved.
[0012]
Further, if the shared cache device is configured as a semiconductor disk cache, the response of the shared cache device is significantly improved as compared with an external storage device such as a hard disk.
[0013]
In addition, if the shared cache device is configured to be provided externally to a plurality of processors, the shared cache device can be easily separated from the processors. Therefore, maintenance such as replacement, repair, and capacity change of the shared cache device can be performed. It can be done quickly and easily.
[0014]
In addition, if the external storage device is provided corresponding to a plurality of processors, a plurality of external storage devices are provided for each processor, so that a load applied to each external storage device can be distributed. Can be. Also, since each processor can simultaneously access and read / write the corresponding external storage device, the processing speed of reading / writing between the processor and the external storage device is improved as a whole.
[0015]
Further, if the shared cache device is configured so as to be able to temporarily store metadata for managing data, address management of data stored in the external storage device and the shared cache device and the use status of the cache area are performed. Metadata such as a cache area link list can be centralized on a shared cache device and unifiedly managed. Therefore, each processor can quickly execute data read / write processing based on the metadata on the shared cache device.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted.
[0017]
(First Embodiment)
Hereinafter, a data management device according to the first embodiment of the present invention will be described.
[0018]
First, an overall configuration of an information management system using a data management device according to the present embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing the overall configuration of an information management system 1 using a data management device 10 according to the present embodiment.
[0019]
As shown in FIG. 1, the information management system 1 according to the present embodiment includes, for example, a plurality of client terminals 3-1, 3-2,..., 3-n (hereinafter, may be referred to as client terminals 3). ) And, for example, one data management device 10 are connected via a network 5. As described above, the information management system 1 is configured as a client / server system in which the client terminal 3 is, for example, a client computer and the data management device 10 is, for example, a server computer. Various services can be provided using the data stored in the device 10.
[0020]
The client terminal 3 is a terminal device for requesting provision of a service, and is, for example, a general-purpose computer such as a personal computer, a mobile terminal such as a portable terminal, a mobile phone, a PHS, a fixed phone, a FAX, or an information home appliance. Be composed. The client terminal 3 includes, for example, an input device (not shown) such as a mouse, a keyboard, and various buttons, and an output device (not shown) such as a monitor and a speaker.
[0021]
Using this input device, the user of the client terminal 3 can input the contents of the requested service to the client terminal 3. When the user's request is input, the client terminal 3 transmits a client request signal to the data management device 10 using a communication device (not shown). The client request signal is, for example, a signal indicating the content of a request from the user, and includes, for example, data information and update data information to be newly registered and their identification information, or identification information of data to be read. Such a client request signal is created by, for example, an application in the client terminal 3 based on a user's input. Note that the client terminal 3 may be configured to automatically transmit a client request signal to, for example, the data management device 10 irrespective of the above-described user input.
[0022]
On the other hand, when the client terminal 3 receives various data transmitted by the data management device 10 using the communication device, the client terminal 3 can output such data to the user using the output device (for example, image display, audio output, and the like).
[0023]
The network 5 is, for example, a dedicated line, the Internet, a LAN (Local Area Network), a WAN (Wide Area Network), a WLL (Wireless Local Loop), a satellite communication network, a telephone network (including a mobile phone network), and a cable. It is composed of various types of public network or dedicated network such as a TV network and a cable broadcasting network, both wired and wireless. When the client terminal 3 and the data management device 10 are provided in, for example, one housing, the network 5 includes a cable corresponding to an interface such as ATA (AT Attachment) or SCSI (Small Computer System Interface) for connecting the both. Shall be considered.
[0024]
The data management device 10 is, for example, a server device that accumulates and stores a large amount of data, and sends out necessary data in response to a request from the client terminal 3, for example, such as a file server, a database server, and a mail server. And so on. For example, the data management device 10 can centrally manage accumulated various data, integrally process correction, update, search, calculation processing, and the like, and can manage a database for protecting data. The data management device 10 is configured as a cluster system in which a plurality of processors and the like are clustered, and details will be described later.
[0025]
The information management system 1 configured as described above provides the data management device 10 with various services for storing, transmitting, transferring, processing, or providing various information based on a request from the client terminal 3. Can be. Examples of this service include, for example, a media information management service for providing, managing, and distributing large-capacity media information such as moving images, music, and text information, an electronic mail service, and various types of information such as consumer information and marketing information. Services to search and analyze.
[0026]
Next, the configuration of the data management device 10 according to the present embodiment will be described in detail with reference to FIG. FIG. 2 is a block diagram illustrating a configuration of the data management device 10 according to the present embodiment.
[0027]
As shown in FIG. 2, the data management device 20 includes, for example, two processors P1 and P2 (hereinafter, also referred to as a processor P) and, for example, two external processors P1 and P2 provided in correspondence with the processors P1 and P2. The storage device includes storage devices ES1 and ES2 (hereinafter, also referred to as an external storage device ES) and a shared cache device SC which is a major feature of the present embodiment.
[0028]
<Processor>
The processor P is a processing device that performs various processes such as a data write process and a data read process with respect to the external storage device ES and the shared cache device SC, and includes, for example, a computer.
[0029]
Here, the configuration of the processor P will be described in more detail with reference to FIG. FIG. 3 is a block diagram illustrating a configuration of the processor P according to the present embodiment.
[0030]
As shown in FIG. 3, the processor P includes a transmission / reception unit 21, a read processing unit 22, a write processing unit 23, a processing request unit 24, a control unit 25, and a storage unit 26.
[0031]
The transmission / reception unit 21 has a function of transmitting / receiving various types of information to / from the outside and other processors P via, for example, the network 5, the communication line 11, and the input / output channels 12 and 13. For example, the transmitting / receiving unit 21 receives a client request signal from the client terminal 3 via, for example, the network 5 and transmits the read data to the client terminal 3. The transmission / reception unit 21 transmits / receives data to be read / written to / from the external storage device ES and the shared cache device SC. Further, the transmission / reception unit 21 transmits / receives a processing request signal described later to / from another processor P.
[0032]
The read processing unit 22 has a function of reading data from the shared cache device SC or the external storage device ES. More specifically, the read processing unit 22 determines whether the data requested to be read is cached in the shared cache device SC based on a data management table described later. The data is read from the device SC and sent to the client terminal 3. On the other hand, if the data is not cached, after specifying the storage destination external storage device ES, the data is read from the external storage device ES onto the shared cache device SC, cached, and then transmitted to the client terminal 3. Send out.
[0033]
The above-described read processing from the external storage device ES may be performed by the read processing unit 22 of the other processor P by requesting the other processor P, but the details will be described later. In addition, the read processing unit 22 determines, for example, based on the data management table whether or not the data requested to be read actually exists, or determines the free state of the shared cache device SC and secures a free area. , Has a function of updating the data management table and the like with respect to the read data, and details thereof will be described later.
[0034]
The write processing unit 23 has a function of writing data to the shared cache device SC or the external storage device ES. This writing processing includes, for example, both writing processing of new data and writing processing for updating existing data. More specifically, when updating the existing data, the write processing unit 23 determines whether or not the data requested to be written is cached in the shared cache device SC based on a data management table described later. If cached, the data on the shared cache device SC is overwritten first. On the other hand, if the existing data is not cached, the data is written after securing an empty area on the shared cache device SC. Further, the write processing unit 23 stores the data written in the shared cache device SC and the new data in, for example, any one external storage device ES (in the case of existing data, the external storage device ES originally stored). Write and store. Therefore, for example, the same data is not written to a plurality of external storage devices ES.
[0035]
The above-described write processing to the external storage device ES may be performed by the write processing unit 23 of the other processor P by requesting the other processor P, but the details will be described later. The write processing unit 23 also has, for example, a function of determining whether or not the data requested to be written actually exists based on the data management table, and a function of updating the data management table and the like for the written data. Details of these will be described later.
[0036]
The processing request unit 24 requests the other processor P to perform a process of reading data from the external storage device ES connected to the other processor P or a process of writing data to the external storage device ES. Having. In this request processing, the processing request unit 24 of a certain processor P creates a signal (hereinafter, referred to as a processing request signal) for requesting the writing processing or the reading processing, and transmits the processing request signal via the communication line 11. This is executed by transmitting to another processor P. As an example of a case where such a request process occurs, for example, when the processor P1 processes a write request received from the client terminal 3, the write processing unit 23 of the processor P1 sends the data to the shared cache device SC. Can be written to the external storage device ES2, but cannot be written to the external storage device ES2. Therefore, the processing request unit 24 of the processor P1 sends the data cached in the shared cache device SC to the write processing unit 23 of the processor P2. For example, there is a case where an instruction to write and store the data in the corresponding area is given.
[0037]
The functions of the read processing unit 22, the write processing unit 23, and the processing request unit 24 as described above may be realized by, for example, application software installed in the processor P.
[0038]
The control unit 25 includes, for example, a CPU (Central Processing Unit) and has a function of controlling each unit of the processor P. The control unit 25 controls, based on, for example, a computer program stored in the storage unit 26 so that the above-described units of the processor P can perform the above-described functions. In addition, by suitably constructing such a computer program according to a process to be executed, the processor P can have not only the above but also various processing functions.
[0039]
The storage unit 26 stores, for example, a main storage device such as various types of ROM (Read Only Memory) and RAM (Random Access Memory), a relatively small-capacity cache memory required for executing a program, and the above-described program. For example, the storage device is constituted by an auxiliary storage device such as a hard disk. Therefore, for example, it does not have a large-capacity disk cache as provided in a processor of a conventional data management device.
[0040]
The configuration of one processor P has been described above. Next, the connection state between the processors P will be described.
[0041]
In the data management device 10 according to the present embodiment, as shown in FIG. 2, for example, two processors P1 and P2 are, for example, via a communication line 11 (including both a wired line and a wireless line) which is an external bus. They are connected in parallel. That is, the independently operable processors P1 and P2 are clustered, and from the viewpoint of the client side, the image is as if there is one large processor (server) as a whole.
[0042]
By thus clustering the plurality of processors P and configuring the data management device 10 as a cluster system, it is possible to improve the reliability of the entire system and improve the performance. That is, for example, even if a failure occurs in one processor P, another processor P takes over the processing, so that the entire system can continue to operate without being down. Also, by responding to requests from many client terminals 3 by a plurality of processors P that operate independently, the load on one processor P can be distributed. Becomes possible.
[0043]
Further, the communication line 11 connecting a plurality of processors P, for example, is not used for transferring data itself, but functions as a control line for mutually requesting processing. That is, the two processors P only transmit and receive the processing request signal, for example, to and from each other via the communication line 11, and need to transmit and receive a large amount of data between the processors as in a conventional data management device. There is no. This is because a plurality of processors P share the shared cache device SC, and therefore it is not necessary to maintain consistency between cache devices as in the related art. For this reason, the processing speed of the data management device 10 becomes higher, and this is very useful especially when the data handled by the data management device 10 is large-volume data with a high update frequency.
[0044]
In the present embodiment, for example, the two processors P1 and P2 are configured, for example, as one spatially independent device (for example, a computer). However, the present invention is not limited to such an example, and the processor P may be in any form as long as it has the processing functions as described above. For example, a plurality of processors P are provided on, for example, one board, or each processor P is configured as, for example, a board that can be inserted into and removed from one housing and housed in one housing. It may be spatially integrated as one piece of hardware. In this case, the communication line 11 can be, for example, an internal bus.
[0045]
<External storage device>
The external storage device ES (External Storage) is, for example, a disk storage device including a hard disk, an optical disk such as a CDROM, a DVD, or the like, and can store a large amount of data and programs. In the present embodiment, for example, one such external storage device ES is provided for each of the plurality of processors P, for example. Specifically, an external storage device ES1 is provided corresponding to the processor P1, and an external storage device ES2 is provided corresponding to the processor P2.
[0046]
The external storage devices ES1 and ES2 are externally attached to the processors P1 and P2 via, for example, input / output channels 12-1 and 12-2 (hereinafter, also referred to as input / output channels 12). I have. The input / output channel 12 is a data communication path connecting the external storage device ES and the processor P. For example, the input / output channel 12 is used for an interface such as ATA (AT Attachment), SCSI (Small Computer System Interface), and USB (Universal Serial Bus). This is an external bus that is connected by a compatible cable. Since the external storage device ES is externally attached in this manner, the processor P and the external storage device ES can be easily separated from each other, so that the external storage device ES can be quickly replaced, repaired, or changed in capacity. . However, the present invention is not limited to such an externally attached example, and the external storage device ES may be built in the processor P.
[0047]
The data necessary for the data management device 10 to execute the service is stored in the external storage device ES having such a configuration. At this time, the data is stored in one of the external storage devices ES1 and ES2. The point is characteristic. Therefore, the same data is not stored in both the external storage devices ES1 and ES2, so that the utilization efficiency of the external storage device ES can be improved. The external storage device ES is managed by, for example, a general computer file system, and the data is managed by, for example, a file format.
[0048]
<Shared cache device>
The shared cache device SC is, for example, a device provided with a cache memory or the like that can be accessed at high speed in a box-shaped casing. The cache memory is configured by a semiconductor memory such as an SRAM (Static Random Access Memory). The shared cache device SC caches (temporarily stores) data necessary for the data management device 10 to execute a service, and reduces data transmission loss between the processor P and the external storage device ES. For example, it functions as a disk cache. The disk cache composed of such a semiconductor memory has a response characteristic that is, for example, ten times or more faster than the external storage device ES composed of a hard disk or the like.
[0049]
For example, in a database server or the like, by increasing the capacity of the disk cache and caching the data stored in the external storage device as much as possible, it is possible to read / write requested data at high speed. . From this viewpoint, the shared cache device SC according to the present embodiment has, for example, a very large capacity, for example, several tens of GB (gigabytes). For this reason, if the large-capacity shared cache device SC is configured to cache, for example, most of the data stored in the plurality of external storage devices ES, the processor P can, for example, transfer the data from the low-speed external storage device ES. Data can be read at high speed using only the shared cache device SC without reading out almost any data.
[0050]
Hereinafter, features of the shared cache device SC according to the present embodiment will be further described.
[0051]
First, the shared cache device SC is provided, for example, externally to the processor P, and is characterized in that it is hardware that is, for example, spatially independent from the processor P. That is, in the conventional data management device, as shown in FIGS. 12 and 13, the cache device is built in the processor and provided around the CPU. On the other hand, as shown in FIG. 2, the shared cache device SC according to the present embodiment is configured separately from the processor P in hardware, for example, as if it were a part of the main storage device of the processor P. Of the external storage device.
[0052]
The shared cache device SC and the processor P are connected via, for example, an input / output channel 13 which is an external bus. The input / output channel 13 connects, for example, a plurality of input / output terminals (not shown) provided in the shared cache device SC to input / output terminals (not shown) of each processor P, and performs high-speed transmission. (For example, a transmission speed of 2.5 Gbps). Therefore, the processor P can access the shared cache device SC via the input / output channel 13 at high speed. Therefore, the transmission loss due to the external attachment of the shared cache device SC can be sufficiently reduced, so that the shared cache device SC can suitably function as, for example, a disk cache. As a data transmission standard of the input / output channel 13, for example, an InfiniBand standard that can realize high-speed serial data transfer between a server and a storage using an optical fiber and a switching technology may be used.
[0053]
As described above, since the shared cache device SC is externally attached to the processor P, for example, maintenance such as replacement, repair, capacity change of the shared cache device SC, and design change of the data management device 10 can be performed quickly and easily. Become. Note that the shared cache device SC is not necessarily limited to the external example as described above. For example, the configuration is such that the shared cache device SC is built in any one of the processors P, and the other processors P are connected to this processor P via an external bus and can access the built-in shared cache device SC. May be.
[0054]
Second, the shared cache device SC is characterized in that it is shared by a plurality of processors P. That is, in the conventional data management device, as shown in FIGS. 12 and 13, a plurality of cache devices are provided corresponding to each processor, and data cached between the plurality of cache devices is further provided. Need to be consistent. On the other hand, in the present embodiment, the shared cache device SC is shared by the processors P1 and P2 connected by the input / output channels 13-1 and 13-2 as shown in FIG. For example, only one is provided. Therefore, the plurality of processors P can read and write data by accessing the same cache device (that is, the shared cache device SC), for example, simultaneously.
[0055]
For this reason, it is not necessary to maintain consistency between a plurality of cache devices as in the related art, so that a plurality of processors P do not exchange data via the communication line 11 when data is updated, for example. I'm done. Accordingly, since the communication amount between the processors P is drastically reduced, the processing speed of each processor P is improved, and the throughput of the entire system is increased. Further, it is possible to provide the data management device 10 having a high effect of increasing the processing capacity when the number of processors P is increased and having excellent expandability.
[0056]
Further, since the redundancy that the same data is cached in different cache devices can be eliminated, the use efficiency of the cache memory increases. In addition, since there is only one shared cache device SC and data is stored in any one of the external storage devices ES as described above, data transfer between the cache memory and the external storage device ES is not performed. For example, it may be performed only once. For this reason, the transfer amount of the same data between the cache memory and the external storage device ES is reduced, so that the load on the external storage device ES can be reduced.
[0057]
In addition, a large-capacity cache device of, for example, a 128 GB class is very expensive (a single device may cost several hundred million yen or more, for example). The cost required to build the management device becomes enormous. On the other hand, in the data management device 10 according to the present embodiment, for example, only one shared cache device SC needs to be provided as a cache device, so that the cost can be significantly reduced as compared with the related art.
[0058]
Next, a configuration example of information cached in the above-described shared cache device SC will be described with reference to FIG. FIG. 4 is an explanatory diagram schematically illustrating a configuration example of information cached in the shared cache device SC according to the present embodiment.
[0059]
As shown in FIG. 4, the cache area of the shared cache device SC stores, for example, a processing data cache area 40 in which data to be actually processed is cached and metadata required for operation of the data management apparatus 10. And the metadata cache area 50.
[0060]
The processing data cache area 40 is an area in which data (actual processing data) provided as a service by the data management apparatus 10 is cached, and occupies, for example, most of the capacity of the cache area. By caching data in the processing data cache area 40, the shared cache device SC can function as a disk cache for reducing data transmission loss between the processor P and the external storage device ES.
[0061]
The processing data cache area 40 is divided into, for example, N cache areas CA1 to CAn-1 (hereinafter, also referred to as a cache area CA). The capacity of each cache area CA is, for example, 64 KB (kilobytes) and is, for example, a fixed size. Each cache area CA is assigned an area number (0 to n-1) in order from the top, and the cache area CA is referred to using the area number. One piece of data to be cached is cached in one cache area CA if the size fits in one cache area CA, and is cached across a plurality of cache areas CA if the size is larger than one cache area CA. .
[0062]
The metadata cache area 50 is an area in which metadata necessary for managing the data is cached. The metadata includes, for example, a data management table MD1, a cache area use status bitmap MD2, and a cache area list MD3. Hereinafter, for example, the three metadata will be described in detail.
[0063]
First, the data management table MD1 according to the present embodiment will be described with reference to FIG. FIG. 5 is an explanatory diagram schematically showing the structure of the data management table MD1 according to the present embodiment.
[0064]
As shown in FIG. 5, the data management table MD1 is a table that holds information for identifying and managing all data existing in the data management device 10. The data management table MD1 is, for example, a group of fixed-length records, and, for example, one record entry corresponds to, for example, one data. Therefore, in the example of FIG. 5, for example, m records are registered, so that, for example, m data exists in the data management device 10.
[0065]
In the record entry, for example, attributes such as (1) data name, (2) host name, (3) file name, (4) last access time, (5) head position of the cache area list, and the like exist. , Various information about the corresponding data is stored.
[0066]
(1) Data name
The data name is a data name given from the client terminal 3, and is, for example, an arbitrary character string. Note that it is not allowed that the same name exists in one data management device 10.
[0067]
(2) Host name
The host name is the name of the processor P connected to the external storage device ES in which data is stored. Processing such as copying data between the external storage device ES and the shared cache device SC is the role of the processor P connected to the external storage device ES. The host name is used to identify which processor P is in charge of this processing.
[0068]
▲ 3 ▼ File name
The file name is a name of a file on the external storage device ES in which the data is recorded.
[0069]
▲ 4 ▼ Last access time
The last access time is the time at which any one of the client terminals 3 last accessed some data. When the processing data cache area 40 runs short, data to be deleted from the processing data cache area 40 is determined based on the last access time.
[0070]
(5) Top position of cache area list
The head position of the cache area list is a value (area number) that records the position of the head entry of a cache area list MD3 described later. If this value is, for example, a negative value, it means invalid, meaning that the information of the data does not exist in the cache area list MD3.
[0071]
By providing such a data management table MD1, all data in the data management device 10 can be unifiedly managed without leakage or duplication.
[0072]
Next, the cache area use status bitmap MD2 according to the present embodiment will be described with reference to FIG. FIG. 6 is an explanatory diagram schematically showing the configuration of the cache area use status bitmap MD2 according to the present embodiment.
[0073]
As shown in FIG. 6, the cache area use status bitmap MD2 holds information indicating whether or not each cache area CA obtained by dividing the processing data cache area 40 into, for example, n pieces is used. . In FIG. 6, whether or not each cache area CA is used is represented by white circles and black circles for convenience of description, but is actually represented by, for example, a 1-bit flag (for example, unused bits). "0" if present, "1" if in use, etc.). Therefore, the cache area use state bitmap MD2 is, for example, an n-bit bitmap in order to indicate the use state of the entire processing data cache area 40. Further, since the relative position from the head of each bit of the cache area use status bit map MD2 corresponds to the area number (0 to n-1) of each divided cache area CA, the use state of any cache area CA Can be identified. For example, in the example of FIG. 6, the bit at the first position (the leftmost black circle in FIG. 6) indicates the use status of the cache area CA1.
[0074]
By providing such a cache area use state bitmap MD2, the use state of the processing data cache area 40 can be centrally managed, so that the time required to search for a free area when caching data can be reduced.
[0075]
Next, the cache area list MD3 according to the present embodiment will be described with reference to FIG. FIG. 7 is an explanatory diagram schematically showing the configuration of the cache area list MD3 according to the present embodiment.
[0076]
As shown in FIG. 7, the cache area list MD3 holds information indicating which position in one data is cached in the cache area CA.
[0077]
If the data capacity is too large to fit in one cache area CA, a plurality of cache areas CA are allocated to one piece of data. In such a case, it is necessary to link a plurality of cache areas CA which are cache destinations for one data. Therefore, a cache area list MD3 is provided in the form of a link list as shown in FIG.
[0078]
In the cache area list MD3, for example, n entries are provided corresponding to, for example, the n cache areas CA as described above. That is, the total number of entries in the cache area list MD3 is equal to, for example, the total number of divisions of the processing data cache area 40. Further, the cache area CA corresponding to the entry can be represented by the relative position from the head of the entry on the cache area list MD3. That is, the k-th entry from the beginning of the cache area list MD3 has information on data held in the cache area CAk (the cache area CA with the area number k).
[0079]
One entry of the cache area list MD3 has attributes such as (1) data position, (2) data size, (3) previous entry position, (4) next entry position, and the like. Link information about data is recorded.
[0080]
(1) Data position
The data position is information indicating which part of one data is cached in the cache area CA corresponding to the entry, and is represented by a relative position from the head of the data of the part. The unit of this data position is the division size of the processing data cache area 40 (the size of one cache area CA), for example, 64 KB. That is, for example, in a case where data of 256 KB is cached separately in, for example, four cache areas CA, for example, the data position of the first entry is “0” × 64 KB, and the data position of the next entry is “ 1 ”× 64 KB, and the data position of the next entry is“ 2 ”× 64 KB.
[0081]
(2) Data size
The data size indicates the effective data size of the data portion held in the cache area CA corresponding to the entry. Normally, this value is the size of one cache area CA, that is, for example, 64 KB, but may be smaller than the size of one cache area CA at the end of the entire data.
[0082]
(3) Previous entry position, (4) Next entry position
The previous entry position and the next entry position are information for constructing a linked list, and represent an entry position before the entry and a next entry position. Specifically, the previous entry position indicates the position of the entry corresponding to the cache area CA holding the part immediately before the data part held by the cache area CA corresponding to the entry. The next entry position indicates the position of the entry corresponding to the cache area CA holding the part immediately after the data part held by the cache area CA corresponding to the entry. Note that the entry position is a numerical value indicating the number of the entry from the top of the cache area list MD3 as described above.
[0083]
The previous entry position and the next entry position will be described in more detail with specific examples. For example, it is assumed that one piece of data is cached in the cache area CA0, the cache area CA3, and the cache area CA7 in this order. In this case, for the entry corresponding to the cache area CA3, its own entry position is “3”, the previous entry position is “0”, and the next entry position is “7”.
[0084]
When such a previous entry position has an invalid value (for example, a negative value), it indicates that the entry is the first entry. When the next entry position has an invalid value (for example, a negative value), it indicates that the entry is the last entry.
[0085]
By providing such a cache area list MD3, for example, one piece of data can be distributed and cached in a plurality of cache areas CA, so that free space can be reduced and the cache memory can be used efficiently.
[0086]
<Processing operation of data management device>
Next, the processing operation of the data management device 10 having the above configuration will be described. Hereinafter, as typical examples of the processing of the data management apparatus 10, three processings of creating new data, writing existing data, and reading existing data will be described in detail. In the following description of the processing method, an example in which a request from the client terminal 3 connected to the processor P1 is processed will be described. However, processing of a request from the client terminal 3 connected to the processor P2 is substantially the same. It is processed according to the following procedure.
[0087]
<Create new data>
First, a process of creating new data in the data management device 10 according to the present embodiment will be described with reference to FIG. FIG. 8 is a flowchart illustrating an operation flow of a new data creation process of the data management apparatus 10 according to the present embodiment.
[0088]
As shown in FIG. 8, first, in step S100, the processor P1 determines whether data having the same data name as the data to be newly created exists (step S100). When newly creating data in response to a request from the client terminal 3 connected to the processor P1, the processor P1 determines whether data having the same name already exists in the system. This determination is executed by the write processing unit 23 of the processor P1, for example, sequentially taking out record entries of the data management table MD1 and comparing the data name designated by the client terminal 3 with all existing data names. Is done. If data having the same data name exists, the process proceeds to step S101, for example, an error indicating that the data name is duplicated is returned to the client terminal 3, and the operation flow ends. On the other hand, if there is no data having the same data name, the process proceeds to step S102.
[0089]
Next, in step S102, a new entry is created on the data management table MD1 (step S102). The write processing unit 23 of the processor P1 accesses the shared cache device SC and secures a new entry in the data management table MD1. At this point, the cache area CA is not newly assigned to the data.
[0090]
Further, in step S104, the processor P1 inquires of the processor P2 about the capacity of the external storage device ES2 (step S104). The write processing unit 23 of the processor P1 inquires of the processor P2 about the free space of the external storage device ES2 connected to the processor P2. This inquiry is performed, for example, in a format in which the write processing unit 23 transmits a free space inquiry signal to the processor P2 via the communication line 11 and receives a response signal from the processor P2.
[0091]
Thereafter, in step S106, the processor P1 determines which external storage device ES is free (step S106). By the inquiry in step S104, the processor P1 can acquire information on the free space of the external storage device ES2. Further, the free space of the external storage device ES1 connected to itself is confirmed by itself and known. Therefore, the write processing unit 23 of the processor P1 can compare which of the free space of the external storage device ES1 and the free space of the external storage device ES2 is larger. As a result, when it is determined that the free space of the external storage device ES1 is large, the process proceeds to step S108, and when it is determined that the free space of the external storage device ES2 is large, the process proceeds to step S110.
[0092]
Next, in step S108, the data is stored in the external storage device ES1 (step S108). The write processing unit 23 of the processor P1 creates a new file in the external storage device ES1, and assigns the file to the data. As a result, the newly created data is stored in the external storage device ES1.
[0093]
On the other hand, in step S110, the data is stored in the external storage device ES2 (step S110). The processing request unit 24 of the processor P1 requests the processor P2 to write the data to the external storage device ES. Upon receiving this request, the write processing unit 23 of the processor P2 creates a new file in the external storage device ES2 and allocates this file to the data.
[0094]
Thereafter, in step S112, the contents of the data management table MD1 are set (step S112). The processor P1 sets the record entry of the data management table MD1 newly created in step S102 to the initial state, and ends the new data creation processing. The initial state of the record entry of the data management table MD1 is, for example, as follows.
(1) Data name = specified data name
{Circle around (2)} host name = name of processor P corresponding to external recording device ES storing data
{Circle around (3)} File name = file name on external recording device ES assigned to data
(4) Last access time = time when this entry was initialized
(5) Head position of cache area list = -1 (invalid)
At the time of creating new data as described above, the data is stored in the external storage device ES, but is not cached in the shared cache device SC, for example.
[0095]
<Write processing of existing data>
Next, a process of writing existing data in the data management device 10 according to the present embodiment will be described with reference to FIG. FIG. 9 is a flowchart illustrating an operation flow of the existing data write processing of the data management apparatus 10 according to the present embodiment.
[0096]
As shown in FIG. 9, first, in step S200, the processor P1 determines whether there is data having the same data name as the specified data name (step S200). When updating existing data in response to a request from the client terminal 3 connected to the processor P1, the processor P1 determines whether or not data with the specified data name actually exists in the system. This determination is performed by the write processing unit 23 of the processor P1, for example, sequentially taking out the record entries of the data management table MD1 and comparing the data name designated by the client terminal 3 with the existing data name. You. If the data with the same data name does not exist, the process proceeds to step S201, where an error indicating that the data with the specified data name does not exist is returned to the client terminal 3, and the operation flow ends. On the other hand, if data having the same data name exists, the process proceeds to step S202.
[0097]
Next, in step S202, it is determined whether or not the data portion designated to be written is cached in the shared cache device SC. (Step S202). First, the write processing unit 23 of the processor P1 extracts the position of the first entry of the cache area list MD3 from the record entry of the data in the data management table MD1. Next, based on the position of the first entry, while following the link list of the cache area list MD3, the data portion designated to be written (that is, the portion to be updated of the data, and a part or the whole of the data) ) Is cached in the processing data cache area 40 of the shared cache device SC. As a result, if it is determined that the data portion is cached in the processing data cache area 40, the process proceeds to step S212. On the other hand, if it is determined that the data is not cached, the process proceeds to step S204.
[0098]
Further, in step S204, it is determined whether or not there is a free area in the processing data cache area 40 (step S204). The write processing unit 23 of the processor P1 refers to the cache area use status bitmap MD2 to determine whether, for example, there is free space in the processing data cache area 40 to cache the data. As a result, when it is determined that there is a free space, the process proceeds to step S208, and when it is determined that there is no free space, the process proceeds to step S206.
[0099]
Thereafter, in step S206, the old cache area CA on the processing data cache area 40 is released (step S206). The write processing unit 23 of the processor P1 detects, for example, data that has not been accessed for the longest time based on the last access time in the entry of the data management table MD1, and discards the data from the cache area CA. As a result, one or more cache areas CA in which the old data is cached are released, and a space is generated in the processing data cache area 40.
[0100]
Next, in step S208, a cache area CA for writing the data is secured in the processing data cache area 40 (step S208). From the cache area CA that was originally free or the cache area CA that has become free in step S206, one or more cache areas CA having a capacity for writing the data are secured. The write processing unit 23 newly allocates the cache area CA to the data.
[0101]
Further, in step S210, an entry on the cache area list MD3 is newly added or updated. (Step S210). The write processing unit 23 of the processor P1 adds, for example, an entry to the cache area list MD3 or updates information inside the existing entry in accordance with the allocation of the new cache area CA to the data in step S208. By doing so, the cache area list MD3 is reset to the one corresponding to the data.
[0102]
Thereafter, in step S212, the corresponding data is written in the processing data cache area 40 (step S212). When the data is originally cached, the write processing unit 23 of the processor P1 overwrites the data portion updated on the cache area CA. In addition, when a cache area CA for writing the data is newly secured in step S208, the data is newly written on the cache area CA. By such processing, the data is cached on the shared cache device SC with the updated contents.
[0103]
Next, in step S214, it is specified which file of which external storage device ES the data is stored in (step S214). When the updated data is cached in the shared cache device SC, next, it is necessary to reflect the update on existing data on the external recording device ES. For this reason, the write processing unit 23 of the processor P1 specifies in which file of which external recording device ES the updated data has to be written. This specification is performed based on the host name and the file name in the record entry corresponding to the data in the data management table MD1. When the host name indicates the processor P1, the process proceeds to step S216, and when the host name indicates the processor P2, the process proceeds to step S218.
[0104]
Further, in step S216, the processor P1 updates the data in the external storage device ES1 (step S216). The write processing unit 23 of the processor P1 overwrites the file specified in step S214 with the updated content of the data from the files in the external storage device ES1.
[0105]
On the other hand, in step S218, the processor P2 requested by the processor P1 updates the data in the external storage device ES2 (step S218). The processing request unit 24 of the processor P1 requests the processor P2 to update the data in the external storage device ES2. Upon receiving this request, the write processing unit 23 of the processor P2 overwrites the file specified in step S214 with the updated content of the data from the files in the external storage device ES2.
[0106]
Thereafter, in step S220, the last access time is updated (step S220). For example, the write processing unit 23 of the processor P1 updates the last access time in the record entry of the data management table MD1 when the process of updating data to the external storage device ES in step S216 or step S218 ends.
[0107]
<Read processing of existing data>
Next, a process of reading existing data in the data management device 10 according to the present embodiment will be described with reference to FIG. FIG. 10 is a flowchart illustrating an operation flow of a process of reading existing data in the data management device 10 according to the present embodiment.
[0108]
As shown in FIG. 10, first, in step S300, the processor P1 determines whether there is data having the same data name as the specified data name (step S300). When reading existing data in response to a request from the client terminal 3 connected to the processor P1, the processor P1 determines whether or not data with the specified data name exists in the system. This determination is performed by the reading processing unit 22 of the processor P1 sequentially taking out, for example, record entries of the data management table MD1, and comparing the data name designated by the client terminal 3 with the existing data name. You. If the data with the same data name does not exist, the process proceeds to step S301, where an error indicating that the data with the specified data name does not exist is returned to the client terminal 3, and the operation flow ends. On the other hand, if data having the same data name exists, the process proceeds to step S302.
[0109]
Next, in step S302, it is determined whether or not the data portion designated to be read is cached in the shared cache device SC. (Step S302). First, the read processing unit 22 of the processor P1 extracts the position of the first entry of the cache area list MD3 from the record entry of the data in the data management table MD1. Next, based on the position of the first entry, while following the link list of the cache area list MD3, the data portion designated to be read (that is, the portion to be read out of the data, and part or all of the data) Is cached in the processing data cache area 40 of the shared cache device SC. As a result, if it is determined that the corresponding data portion is not cached in the processing data cache area 40, the process proceeds to step S304. On the other hand, if it is determined that the data is cached, there is no need to read the data from the external storage device ES, so the process proceeds to step S318.
[0110]
Further, in step S304, it is determined whether or not there is a free area in the processing data cache area 40 (step S304). The read processing unit 22 of the processor P1 refers to the cache area use status bitmap MD2 and determines whether or not there is free space in the cache area for processing data 40 to read the data from the external storage device ES and cache it, for example. Is determined. As a result, when it is determined that there is a free space, the process proceeds to step S308, and when it is determined that there is no free space, the process proceeds to step S306.
[0111]
Thereafter, in step S306, the old cache area CA on the processing data cache area 40 is released (step S306). The read processing unit 22 of the processor P1 detects, for example, data that has not been accessed for the longest time based on the last access time in the entry of the data management table MD1, and discards the data from the cache area CA. As a result, one or more cache areas CA in which the old data is cached are released, and a space is generated in the processing data cache area 40.
[0112]
Next, in step S308, a cache area CA for reading the data is secured in the processing data cache area 40 (step S308). From the cache area CA that was originally free or the cache area CA that has become free in step S206, one or more cache areas CA having a capacity for writing the data are secured. The read processing unit 22 newly allocates the cache area CA to the data to be read.
[0113]
Further, in step S310, an entry on the cache area list MD3 is newly added or updated. (Step S310). The read processing unit 22 of the processor P1 adds, for example, an entry to the cache area list MD3 or updates information inside an existing entry in accordance with the allocation of the new cache area CA to the data in step S308. By doing so, the cache area list MD3 is reset to the one corresponding to the data.
[0114]
Then, in step S312, it is specified which file of which external storage device ES stores the specified data (step S312). When the cache area CA in the processing data cache area 40 is secured, next, it is necessary to read the designated data from the external recording device ES into the secured cache area CA. Therefore, the read processing unit 22 of the processor P1 specifies from which file of which external recording device ES the data should be read. This specification is performed based on the host name and the file name in the record entry corresponding to the data in the data management table MD1. If the host name indicates the processor P1, the process proceeds to step S314. If the host name indicates the processor P2, the process proceeds to step S316.
[0115]
Next, in step S314, the processor P1 reads the data from the external storage device ES1 onto the processing data cache area 40 (step S314). The read processing unit 22 of the processor P1 reads the data from the file specified in step S312 in the external storage device ES1, and caches the data in the cache area CA allocated in step S308.
[0116]
On the other hand, in step S316, the processor P2 requested by the processor P1 reads the data from the external storage device ES2 onto the processing data cache area 40 (step S316). The processing request unit 24 of the processor P1 requests the processor P2 to read the data from the external storage device ES2. Upon receiving this request, the read processing unit 22 of the processor P2 reads the data from the file specified in step S312 in the external storage device ES2, and caches the data in the cache area CA allocated in step S308. I do.
[0117]
Further, in step S318, the data in the shared cache device SC is sent to the client terminal 3 (step S318). The read processing unit 22 of the processor P1 sends the data cached in the processing data cache area 40 to the client terminal 3 that has requested the read using the transmission / reception unit 21. The client terminal 3 receiving the data can browse the data using, for example, a predetermined application.
[0118]
Thereafter, in step S320, the last access time is updated (step S320). For example, the read processing unit 22 of the processor P1 updates the last access time in the record entry of the data management table MD1 when the transmission processing in step S318 ends.
[0119]
In the processing operation of the data management device 10 described above, for example, the two processors P1 and P2 cache data in the same shared cache device SC. No need to take. For this reason, there is no need to transfer updated data between processors when updating data, so that the processing speed of the data management device 10 can be improved. Further, since a plurality of copies of the same data are not cached or stored in a plurality of external storage devices ES, the utilization efficiency of the shared cache device SC and the external storage device ES is improved, and the storage capacity of the entire system is improved. Can be reduced. Further, since the number of data transfers between the external storage device ES and the shared cache device SC for copying is small, the load on the external storage device ES is reduced, and the response of the data management device 10 configured as a cluster system is reduced. Can be improved. The above-described effects become more remarkable when the data managed by the data management device 10 is frequently updated and has a large capacity.
[0120]
The preferred embodiment of the present invention has been described with reference to the accompanying drawings, but the present invention is not limited to this example. It is obvious that a person skilled in the art can conceive various changes or modifications within the scope of the technical idea described in the claims, and those changes naturally fall within the technical scope of the present invention. It is understood to belong.
[0121]
For example, the data management device 10 according to the embodiment has a configuration including, for example, two sets of processors P and an external storage device ES. However, the present invention is not limited to this example. As shown in FIG. 11, for example, three or more arbitrary n sets of processors P and an external storage device ES may be provided. At this time, the n processors P may be connected to each other via the communication line 11 and may share, for example, one shared cache device SC connected via the input / output channel 12. With this configuration, a large-scale, for example, server environment can be constructed by clustering more processors P, so that the processing capacity of the data management device 10 is improved, and it is possible to respond to more requests from the client terminals 3. .
[0122]
Further, in the data management device 10 according to the above-described embodiment, the external storage device ES is provided corresponding to each of the plurality of processors P. However, the present invention is not limited to such an example, and the external storage device ES is not necessarily provided. It may not be provided in one-to-one correspondence with the processor P. For example, for example, one large-capacity external storage device ES connected to, for example, only the processor P1 may be provided in the data management device 10. As shown in FIG. 11, a plurality of processors P share, for example, one or more external storage devices ES (that is, the external storage device ES is connected to all the processors P, and any of the processors P (A shared external storage device that can also be accessed from the outside).
[0123]
Further, in the data management device 10 according to the above embodiment, for example, only one shared cache device SC is provided. However, the present invention is not limited to such an example. An SC may be provided to connect each shared cache device SC to each processor P, for example, in parallel. Thereby, the shared cache device SC can be multiplexed to cope with an unexpected failure of the shared cache device SC, so that the reliability of the data management device 10 is improved.
[0124]
In the data management device 10 according to the above embodiment, the plurality of processors P, the shared cache device SC of one, and the plurality of external storage devices ES are separately configured as hardware, but the present invention is not limited to such an example. Not limited. For example, the external storage device ES may be incorporated in the housing of the processor P instead of being externally attached. Further, for example, all of the plurality of processors P, the shared cache device, and the plurality of external storage devices ES are integrated in hardware, for example, provided in one housing or on the same substrate. May be used.
[0125]
In the above-described embodiment, the client terminal 3 which is separately configured as hardware is used as means for requesting the data management device 10 to provide a service (for example, data transmission / reception). It is not limited to. For example, the requesting means may be hardware integrated with the data management device 10, or may be configured by software installed in the data management device 10 or other devices, for example. .
[0126]
In addition, the data management device 10 may include a data processing unit that processes data to be read and written. For example, by providing such a data processing unit, the processor P can perform processing operations such as various calculations, aggregations, and synthesis on data read and written between the external storage device ES and the shared cache device SC. You may. Thus, the data management device 10 provides the client terminal 3 with data processed in a desired mode, or stores the processed data in the external storage device ES, for example, to improve the efficiency of the external storage device ES. Can be planned.
[0127]
【The invention's effect】
As described above, according to the present invention, cache data can be unified by sharing a cache device among a plurality of processors, so that there is no need to transfer data between processors. Therefore, the processing speed of the processor is improved, and the throughput of the entire data management device is improved. Furthermore, since the rate of increase in processing capacity when the number of processors installed is increased, a data management device with excellent expandability can be provided.
[0128]
Further, since multiple copies of the same data are not cached, the utilization efficiency of the cache device can be improved. Further, since the number of data transfers between the external storage device and the cache device is reduced, the load on the external storage device is reduced, and the response of the data management device is improved.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an overall configuration of an information management system 1 in which a data management device according to a first embodiment is used.
FIG. 2 is a block diagram illustrating a configuration of a data management device according to the first embodiment;
FIG. 3 is a block diagram illustrating a configuration of a processor according to the first embodiment;
FIG. 4 is an explanatory diagram schematically illustrating a configuration example of information cached in the shared cache device according to the first embodiment;
FIG. 5 is an explanatory diagram schematically illustrating the structure of a data management table according to the first embodiment;
FIG. 6 is an explanatory diagram schematically illustrating a configuration of a cache area use status bitmap according to the first embodiment;
FIG. 7 is an explanatory diagram schematically illustrating a configuration of a cache area list according to the first embodiment;
FIG. 8 is a flowchart illustrating an operation flow of a new data creation process of the data management device according to the first embodiment;
FIG. 9 is a flowchart illustrating an operation flow of a write process of existing data in the data management device according to the first embodiment;
FIG. 10 is a flowchart illustrating an operation flow of a process of reading existing data in the data management device according to the first embodiment;
FIG. 11 is a block diagram illustrating a modification of the data management device;
FIG. 12 is a block diagram showing a configuration example of a general cluster system applied to a conventional data management device.
FIG. 13 is a block diagram showing a configuration example of a general cluster system applied to a conventional data management device.
[Explanation of symbols]
1: Information management system
3: Client terminal
5: Network
10: Data management device
11: Communication line
12, 13: I / O channel
22: read processing unit
23: Write processing unit
40: Processing data cache area
50: Cache area for metadata
P: Processor
SC: Shared cache device
ES: External storage device
MD1: Data management table
MD2: Cache area usage status bitmap
MD3: Cache area list

Claims (6)

A plurality of processors for performing data write processing and data read processing in response to external requests;
One or more external storage devices in which the data is stored;
A shared cache device shared by the plurality of processors and temporarily storing at least the data read / written to / from the external storage device;
A data management device, comprising: 2. The data management device according to claim 1, wherein the shared cache device is simultaneously accessible by the plurality of processors. The data management device according to claim 1, wherein the shared cache device is a semiconductor disk cache. 2. The data management device according to claim 1, wherein the shared cache device is provided externally to the plurality of processors. 2. The data management device according to claim 1, wherein the external storage device is provided corresponding to the plurality of processors. 2. The data management device according to claim 1, wherein the shared cache device can further temporarily store metadata for managing the data.

Images