JP7044403B2 - Storage system, storage control method and storage control program - Google Patents

Description

The present disclosure relates to storage systems, storage control methods and storage control programs.

In a storage system such as a solid state drive (SSD), it is known to use a memory for read cache in order to speed up the read process. However, the memory for read cache is expensive, and it is difficult to increase the capacity.
Further, the flash memory used for the SSD has a limited writable capacity, and data written in excess of the writable capacity is liable to cause a read error due to deterioration, and the reliability of the written data is lowered.

Therefore, Patent Document 1 discloses a storage system in which a drive having a write count of more than the upper limit is diverted as a cache of hot data stored in a drive having a read speed lower than this.
Further, Patent Document 2 discloses an information storage device that functions as a secondary cache of a data disk device and includes two SSDs having a redundant configuration. When the information storage device described in Patent Document 2 detects an SSD whose write count has reached the threshold value or more, the data of the other SSD is copied to the spare disk device, and the data related to the write request is stored in the buffer memory. Duplicate to a spare disk device via.

Japanese Unexamined Patent Publication No. 2019-113891 JP-A-2015-185133

However, in the storage system described in Patent Document 1, a drive whose number of writes exceeds the upper limit can no longer be used as data storage. Further, when the number of writes of other drives exceeds the upper limit, there is a problem that the reliability of the data written after that cannot be ensured.
Further, the information storage device described in Patent Document 2 requires a buffer memory and a spare disk device in addition to the SSD functioning as a secondary cache, and has a problem that the circuit configuration becomes complicated and large-scale.

An object of the present disclosure is to provide a storage system, a storage control method, and a storage control program that realize improvement of processing performance and prevention of deterioration of data reliability with a simple configuration in view of the above-mentioned problems.

The storage system according to one aspect of the present disclosure includes a storage unit having a first storage area for storing the first data and a second storage area for storing the second data, and the first storage area and the second storage area. On the other hand, it is provided with a storage control unit that controls reading and writing of data according to the mode. The storage control unit is hot data in which the number of reads within a predetermined time is equal to or greater than a predetermined second threshold value in the first mode in which the cumulative write amount of the first storage area is less than a predetermined first threshold value. Is detected in the first data, and a copy of the hot data is stored in the second storage area. Further, the storage control unit receives the data write request to the first storage area in the second mode in which the cumulative write amount of the first storage area is equal to or greater than the first threshold value. The requested data is stored in the second storage area.

In the storage control method according to one aspect of the present disclosure, when the cumulative write amount of the first storage area of the storage unit is less than a predetermined first threshold value, the mode is set to the first mode, and the storage unit is the first. When the cumulative write amount of one storage area is equal to or greater than the first threshold value, the mode is set to the second mode, and in the first mode, the number of reads within a predetermined time is equal to or greater than a predetermined second threshold value. When the data is detected from the first data stored in the first storage area, the duplicate of the hot data is stored in the second storage area of the storage unit, and in the second mode, the first In response to receiving a request to write data to the storage area, the data related to the write request is stored in the second storage area.

The storage control program according to one aspect of the present disclosure causes a computer to execute a storage control method. In the storage control method, when the cumulative write amount of the first storage area of the storage unit is less than a predetermined first threshold value, the mode is set to the first mode, and the cumulative write of the first storage area of the storage unit is performed. When the amount is equal to or greater than the first threshold value, the mode is set to the second mode, and in the first mode, the hot data in which the number of readings within a predetermined time is equal to or greater than the predetermined second threshold value is the first. In response to the detection from the first data stored in the storage area, the duplicate of the hot data is stored in the second storage area of the storage unit, and in the second mode, the data to the first storage area is stored. In response to receiving the write request, the data related to the write request is stored in the second storage area.

INDUSTRIAL APPLICABILITY According to the present disclosure, it is possible to provide a storage system, a storage control method, and a storage control program that realize improvement of processing performance and prevention of deterioration of data reliability with a simple configuration.

It is a block diagram which shows the structure of the storage system (storage apparatus) which concerns on Embodiment 1. FIG. It is a flowchart which shows an example of the processing of the storage apparatus which concerns on Embodiment 1. FIG. It is a block diagram which shows an example of the structure of the storage apparatus which concerns on Embodiment 2 together with a host apparatus. It is a schematic block diagram which shows an example of the hardware configuration of the storage apparatus which concerns on Embodiment 2. FIG. It is a figure which shows an example of the address control table which concerns on Embodiment 2. FIG. It is a figure which shows an example of the read frequency management table which concerns on Embodiment 2. It is a figure which shows an example of the write amount management table which concerns on Embodiment 2. FIG. It is a flowchart which shows an example of the writing process of the storage apparatus which concerns on Embodiment 2. FIG. It is a figure for demonstrating the writing process in the 2nd mode of the storage apparatus which concerns on Embodiment 2. FIG. It is a flowchart which shows an example of the read process of the storage apparatus which concerns on Embodiment 2. It is a flowchart which shows an example of the read process of the storage apparatus which concerns on Embodiment 2. It is a figure which shows typically the storage state at an arbitrary time point in the 1st mode of the 1st storage area and the 2nd storage area which concerns on Embodiment 2. FIG. It is a block diagram which shows an example of the structure of the storage apparatus which concerns on Embodiment 3 together with a host apparatus. It is a flowchart which shows an example of the read process in the 2nd mode of the storage apparatus which concerns on Embodiment 3. FIG.

Hereinafter, the present disclosure will be described through embodiments, but the disclosure relating to the scope of claims is not limited to the following embodiments. Moreover, not all of the configurations described in the embodiments are indispensable as means for solving the problem. In each drawing, the same elements are designated by the same reference numerals, and duplicate explanations are omitted as necessary.

<Embodiment 1>
First, Embodiment 1 of the present disclosure will be described with reference to FIGS. 1 and 2. FIG. 1 is a block diagram showing a configuration of a storage system (hereinafter, referred to as a storage device) 1 according to the first embodiment. The storage device 1 includes a storage unit 12 and a storage control unit 15.

The storage unit 12 is a storage medium having a first storage area 13 and a second storage area 14. Here, the first storage area 13 is a storage area for storing the first data, and the second storage area 14 is a storage area for storing the second data.
The storage control unit 15 controls reading and writing of data to the first storage area 13 and the second storage area 14 according to the mode (control mode).

FIG. 2 is a flowchart showing an example of processing of the storage device 1 according to the first embodiment.
First, in step S10, the storage control unit 15 of the storage device 1 acquires a write request from the outside.
Next, in step S11, the storage control unit 15 determines whether or not the cumulative write amount of the first storage area 13 is less than a predetermined first threshold value. If the storage control unit 15 determines that the cumulative write amount is less than the first threshold value (Yes in step S11), the process proceeds to step S12, and if not (No in step S11), the process proceeds to step S16. ..

In step S12, the storage control unit 15 sets the control mode to the first mode. That is, the first mode is a control mode by the storage control unit 15 when the cumulative write amount of the first storage area 13 is less than the first threshold value.
Next, in step S13, the storage control unit 15 stores the data related to the write request (referred to as write target data) in the first storage area 13 of the storage unit 12.

Next, in step S14, the storage control unit 15 determines whether or not hot data is detected from the first data stored in the first storage area 13. Here, the hot data is data whose read frequency is equal to or higher than a predetermined second threshold value. The read frequency is the number of reads within a predetermined time. If hot data is detected (Yes in step S14), the storage control unit 15 advances the process to step S15, and if not (No in step S14), the storage control unit 15 ends the process.

In step S15, the storage control unit 15 replicates the detected hot data in the second storage area 14.

Further, in step S16, the storage control unit 15 sets the control mode to the second mode. That is, the second mode is a control mode by the storage control unit 15 when the cumulative write amount of the first storage area 13 is equal to or greater than the first threshold value.
Next, in step S17, the storage control unit 15 stores the write target data related to the write request in the second storage area 14 of the storage unit 12. Then, the memory control unit 15 ends the process.

As described above, according to the first embodiment, the storage control unit 15 of the storage device 1 duplicates the hot data in response to the detection of the hot data from the first data in the first storage area 13 in the first mode. Is stored in the second storage area 14. As a result, the second storage area 14 can function as a cache of the first storage area 13, and the read processing can be speeded up. Then, in the second mode, the storage control unit 15 stores the data to be written in the second storage area 14 in response to receiving the request to write the data to the first storage area 13. In this way, the second storage area 14, which functions as a cache of the first storage area 13, also functions as a storage destination of data for ensuring reliability when the cumulative write amount is exceeded. Therefore, the storage device 1 can improve the processing performance and prevent the deterioration of data reliability with a simple configuration.

<Embodiment 2>
Next, Embodiment 2 of the present disclosure will be described with reference to FIGS. 3 to 12. FIG. 3 is a block diagram showing an example of the configuration of the storage device 2 according to the second embodiment together with the host device 4. Here, the host device 4 is a device such as a computer capable of inputting / outputting data to / from the storage device 2. The host device 4 transmits a data read / write request to the storage device 2, acquires data from the storage device 2, or stores the data in the storage device 2.

The storage device 2 is a storage device that performs data read processing or data write processing in response to a request from the host device 4. As shown in this figure, the storage device 2 includes a communication unit 21, a storage unit 22, a storage control unit 25, and a monitoring unit 27.

The communication unit 21 is communicably connected to the host device 4 and transmits / receives data to / from the host device 4.

The storage unit 22 is a non-volatile storage medium such as a solid state drive (SSD) that stores write target data related to a write request from the host device 4. The storage unit 22 has two storage areas, a first storage area 23 and a second storage area 24, which are logically separated from each other by partitioning.

The first storage area 23 is a main data area for storing data designated by the host device 4 in response to a write request. In the second embodiment, the first storage area 23 stores the data designated by the host device 4 by the write request as the first data.

The second storage area 24 is an additional data area used for improving the read processing performance of the storage device 2 and preventing the reliability of the data stored in the storage unit 22 from deteriorating. The second storage area 24 stores at least a part of the first data stored in the first storage area 23. In the second embodiment, the second storage area 24 duplicates at least a part of the data included in the first data, and temporarily stores the duplicate as the second data.

The storage control unit 25 is connected to each component of the storage device 2. The storage control unit 25 corresponds to the control mode for the first storage area 23 and the second storage area 24 in response to the acquisition of the read or write request from the host device 4 via the communication unit 21. Perform a read or write process. In the second embodiment, the storage control unit 25 executes the processing for the first storage area 23 and the second storage area 24 by using the address control table described later.

The monitoring unit 27 monitors and manages the usage status of the storage unit 22. Then, the monitoring unit 27 supplies the storage control unit 25 with information related to the monitoring result. The monitoring unit 27 has a data usage status monitoring unit 28 and a cumulative write amount monitoring unit 29.

The data usage status monitoring unit 28 monitors and manages the usage status of the data stored in the first storage area 23 and the second storage area 24 of the storage unit 22. Here, the data usage status includes the data read frequency, and the data usage status monitoring unit 28 manages information regarding the data read frequency by using the read frequency management table described later.

The cumulative write amount monitoring unit 29 monitors and manages the cumulative write amount of the storage elements constituting the storage unit 22. Here, the cumulative write amount is the size of the cumulative write data written to the storage elements constituting each storage area, but may be the cumulative number of writes to the storage element. In the second embodiment, the cumulative write amount monitoring unit 29 manages information regarding the cumulative write amount of the storage elements constituting each storage area by using the write amount management table described later.

FIG. 4 is a schematic configuration diagram showing an example of the hardware configuration of the storage device 2 according to the second embodiment. In the second embodiment, the storage device 2 is an SSD. The storage device 2 includes an interface 200, an interface controller 205, a buffer memory 210, first and second storage element groups 230 and 240, a storage element control unit 270, a data usage status monitoring unit 280, and a storage element usage status monitoring unit 290. ..

Interface 200 is a storage interface such as a Serial Advanced Technology Attachment (SATA) interface or a Peripheral Component Interconnect Express (PCIe) interface. The interface 200 connects the storage device 2 to the host device 4 so as to be communicable.

The interface controller 205 is a communication controller. The interface controller 205 is electrically connected to the buffer memory 210, the first storage element group 230, the second storage element group 240, and the storage element control unit 270 of the host device 4 and the storage device 2 via the interface 200. The interface 200 and the interface controller 205 function as the communication unit 21 shown in FIG.

The buffer memory 210 is a storage medium that temporarily stores data necessary for writing or reading processing. The buffer memory 210 may be composed of a storage element such as a Dynamic Random Access Memory (DRAM) or a Static Random Access Memory (SRAM).

The first storage element group 230 and the second storage element group 240 function as the storage unit 22 shown in FIG.
The first storage element group 230 has a plurality of first storage elements which are NAND flash memories. As an example in this figure, the first storage element group 230 has a configuration in which k sets of n first storage elements (for example, 230-1 to 230-n) connected in series are connected in parallel (for example, 230-1 to 230-n). n and k are natural numbers). The first storage element group 230 functions as the first storage area 23 shown in FIG.

The second storage element group 240 has a plurality of second storage elements which are NAND flash memories. The second storage element may have the same configuration as the first storage element. As an example in this figure, the second storage element group 240 has a configuration in which n second storage elements 240-1 to 240-n are connected in series. The second storage element group 240 functions as the second storage area 24 shown in FIG.

The storage element control unit 270 is a memory controller that controls the use of the storage elements of the first storage element group 230 and the second storage element group 240 and manages the usage status. The storage element control unit 270 is electrically connected to each component of the storage device 2 and functions as the storage control unit 25 shown in FIG.

The data usage status monitoring unit 280 is a component that monitors and analyzes information regarding the usage status of data written in the storage elements included in the first storage element group 230 and the second storage element group 240 and the access frequency of the data. .. The data usage status monitoring unit 280 functions as the data usage status monitoring unit 28 of the monitoring unit 27 shown in FIG.

The storage element usage status monitoring unit 290 operates in cooperation with the storage element control unit 270, and is a component that monitors and manages the writing amount of the storage elements included in the first storage element group 230 and the second storage element group 240. .. As an example, the storage element usage status monitoring unit 290 may be equipped with a Self-Monitoring, Analysis and Reporting Technology (S.M.A.R.T.) Function. The storage element usage status monitoring unit 290 functions as a cumulative write amount monitoring unit 29 of the monitoring unit 27 shown in FIG.

Although it is assumed that the first storage area 23 and the second storage area 24 are composed of the first storage element group 230 and the second storage element group 240, respectively, data erasure inside the storage element which is a NAND flash memory is erased. It may be composed of block units, which are the minimum units.

Next, various tables used for various processes of the storage device 2 will be described with reference to FIGS. 5 to 7. FIG. 5 is a diagram showing an example of an address control table used by the storage control unit 25 according to the second embodiment in the read / write process. The address control table includes address information (first storage area address) in the first storage area 23 of the data storage destination and address information (second storage area) in the second storage area 24 of the data duplication destination or the duplication storage destination. It is a table that associates with (address). For example, as shown in this figure, the first storage area address "A001" is associated with the second storage area address "B001". That is, this indicates that the duplicate of the data stored in the "A001" of the first storage area 23 is stored in the "B001" of the second storage area 24. On the other hand, the first storage area address "A002" does not have an associated second storage area address. That is, this indicates that the duplicate of the data stored in "A002" of the first storage area 23 is not stored anywhere in the second storage area 24.

As a result, the storage control unit 25 uses the first storage area address of the storage destination of the data related to the read request (referred to as the read target data) to determine whether or not the read target data is also in the second storage area 24. You can check and get its storage location.

As shown in this figure, the address control table may have additional information. For example, the additional information may include the date and time when the data was written to the second storage area address. Further, the additional information may include the update date and time when the address control table is updated due to the write processing related to the write request or the wear leveling.

FIG. 6 is a diagram showing an example of a read frequency management table managed by the data usage status monitoring unit 28 according to the second embodiment. The read frequency management table is a table that associates the first storage area address with the data read frequency. As shown in this figure, for example, the frequency of reading the data whose storage destination is the first storage area address "A001" is "10" times, and the reading frequency of the data whose storage destination is the first storage area address "A002" is read. The frequency is "0" times.
The data usage status monitoring unit 28 determines the frequency of reading the data of the first storage area address associated with the read second storage area address in response to the data being read from the second storage area 24. Increment. Further, the data usage status monitoring unit 28 may update the read frequency of the data of the erased first storage area address to "0" in response to the data being erased from the first storage area 23. Further, when the first storage area address is reassigned, the data usage status monitoring unit 28 inherits the read frequency of the data of the immediately preceding first storage area address as the read frequency of the data of the new first storage area address. It's fine.

FIG. 7 is a diagram showing an example of a write amount management table managed by the cumulative write amount monitoring unit 29 according to the second embodiment. The write amount management table is a table that associates the type of storage area with the cumulative write amount. In this figure, the write amount management table may additionally associate the element identification information (element ID), the address information, and the individual cumulative write amount.

The element ID is identification information that identifies the storage elements constituting the first storage element group 230 and the second storage element group 240 that function as the first storage area 23 and the second storage area 24.
The address information is the first storage area address when the storage area is the first storage area 23, and indicates the second storage area address when the storage area is the second storage area 24.
The individual cumulative write amount indicates the cumulative write amount for each storage element.

The cumulative write amount monitoring unit 29 updates the individual cumulative write amount according to the execution of the write process, and sets the total of the individual cumulative write amounts as the cumulative write amount of the storage elements constituting the storage area. The write amount management table may be updated.

Next, the writing process of the storage device 2 will be described with reference to FIGS. 8 to 9. FIG. 8 is a flowchart showing an example of the writing process of the storage device 2 according to the second embodiment. The initial control mode is the first mode.

First, in step S20, the communication unit 21 of the storage device 2 receives a data write request from the host device 4 to the first storage area 23. The communication unit 21 supplies information including the first storage area address of the write request destination to the storage control unit 25. At this time, the communication unit 21 may temporarily store the data designated by the host device 4 in response to the write request in the buffer memory 210 shown in FIG. 4 as the data to be written.

Next, in step S21, the storage control unit 25 refers to the write amount management table of the cumulative write amount monitoring unit 29, and determines whether or not the cumulative write amount of the first storage area 23 is less than the first threshold value. .. In the second embodiment, the first threshold value may be the writable capacity of the first storage area 23, or may be any predetermined value. If the storage control unit 25 determines that the cumulative write amount is less than the first threshold value (Yes in step S21), the process proceeds to step S22, and if not (No in step S21), the process proceeds to step S26. ..

Next, in step S22, the storage control unit 25 continues to set the control mode to the first mode.

Next, in step S23, the storage control unit 25 stores the write target data in the first storage area address of the write request destination in the first storage area 23.

In step S26, the storage control unit 25 sets the control mode to the second mode according to the fact that the cumulative write amount is not determined to be less than the first threshold value in step S21.

Next, in step S27, the storage control unit 25 stores the data to be written in the first storage area 23 and the second storage area 24. At this time, the storage control unit 25 stores the data to be written in the first storage area address of the write request destination, allocates the second storage area address corresponding to the first storage area address, and assigns the second storage area address to the allocated second storage area address. The data to be written may be duplicated.

Then, in step S28, the storage device 2 updates various related tables. For example, the storage control unit 25 requests the cumulative write amount monitoring unit 29 to update the write amount management table in the first mode. Further, the storage control unit 25 updates the address control table in the second mode, and requests the cumulative write amount monitoring unit 29 to update the write amount management table. Then, the cumulative write amount monitoring unit 29 updates the write amount management table in response to the request of the storage control unit 25.

As described above, in the first mode, the storage control unit 25 stores the data to be written in the first storage area 23 in response to receiving the request to write the data to the first storage area 23. Further, in the second mode, the storage control unit 25 stores the data to be written in the first storage area 23 and the second storage area 24 in response to receiving the data write request to the first storage area 23. As a result, the second storage area 24 functions as a redundant storage area for data related to the Write command issued after the cumulative write amount is exceeded, and the reliability of the command can be prevented from deteriorating.

Instead of step S21, the storage control unit 25 determines whether or not there is a first storage element having an individual cumulative write amount of less than a predetermined threshold among the first storage elements constituting the first storage area 23. You may. In this case, when the storage control unit 25 determines that the individual cumulative write amount is less than the predetermined threshold value, the process may proceed to step S22, and when not, the process may proceed to step S26.

Here, the storage control unit 25 may selectively erase a part of the data already stored in the second storage area 24 in parallel with the process shown in step S27. FIG. 9 is a diagram for explaining a write process in the second mode of the storage device 2 according to the second embodiment. This figure schematically shows the storage state of the second storage area 24, and the second storage area 24 before and after the selective erasing process is described as “24a” and “24b”, respectively. For example, it is assumed that the data of "Data-1", "Data-2" and "Data-3" are stored in the second storage area addresses "B001", "B002" and "B003" shown in this figure, respectively. do. Here, "Data-1" of the second storage area address "B001" and "Data-2" of "B002" have an old writing date and time, and the reading frequency at this point is equal to or less than the second threshold value described later. Suppose it is some data. In this case, the storage control unit 25 may refer to the address control table and the read frequency management table of the data usage status monitoring unit 28, and delete "Data-1" and "Data-2" from the second storage area 24. .. Then, the storage control unit 25 may reassign the second storage area address to the remaining data in the second storage area 24. After that, the storage control unit 25 updates the address control table.

In this way, the storage control unit 25 selectively erases the data stored in the second storage area 24 in the second mode based on at least one of the writing time and the reading frequency, and the second storage area 25. The data stored in 24 is organized. The main rearranging process may be performed at any time in the second mode. Further, this rearranging process may be performed at any time in the first mode.

As a result, the storage device 2 can contribute to speeding up the reading process or ensuring the reliability of the stored data while minimizing the amount of data in the second storage area 24. In particular, in the second mode, the second storage area 24 stores new data each time a new write request is made, so that the amount of data in the second storage area 24 rapidly increases. Therefore, in the second mode, the effect of ensuring the reliability of the stored data in a predetermined amount while minimizing the amount of data in the second storage area 24 can be remarkably obtained.
In the second embodiment, the data erased from the second storage area 24 in the main rearranging process is stored as the original data in the first storage area 23, so that the disadvantage due to the erasure is small.

Next, the read process of the storage device 2 will be described with reference to FIGS. 10 to 12. 10 and 11 are flowcharts showing an example of the read process of the storage device 2 according to the second embodiment.

First, in step S30, the communication unit 21 of the storage device 2 receives a data read request from the host device 4 to the first storage area 23. The communication unit 21 supplies information including the first storage area address of the read request destination to the storage control unit 25.

Then, in step S31, the storage control unit 25 requests the data usage status monitoring unit 28 to update the read frequency management table. As a result, the data usage status monitoring unit 28 increments the read frequency of the data associated with the first storage area address of the read request destination in the read frequency management table.

Next, in step S32, the storage control unit 25 determines whether or not the control mode is the first mode. If the memory control unit 25 determines that the control mode is the first mode (Yes in step S32), the process proceeds to step S33, and if not (No in step S32), the process proceeds to step S39.

In step S33, the storage control unit 25 determines whether or not the data to be read is stored in the second storage area 24. At this time, the storage control unit 25 refers to the address control table and determines whether or not there is a second storage area address associated with the first storage area address of the read request destination, thereby setting the second storage area 24. It may be determined whether or not the data to be read is stored. If the storage control unit 25 determines that the data to be read is stored in the second storage area 24 (Yes in step S33), the process proceeds to step S37, and if not (No in step S33), the process is performed. Proceed to step S34.

In step S34, the storage control unit 25 acquires the data to be read from the first storage area 23. The storage control unit 25 may temporarily store the data to be read in the buffer memory 210 shown in FIG.

In step S35, the storage control unit 25 determines whether or not the read frequency of the read target data is less than the second threshold value. At this time, the storage control unit 25 may refer to the read frequency management table of the data usage status monitoring unit 28 and acquire information regarding the read frequency of the data to be read. If the storage control unit 25 determines that the read frequency of the data to be read is less than the second threshold value (Yes in step S35), the process proceeds to step S38, and if not (No in step S35), the process is stepped. Proceed to S36.

In step S36, the storage control unit 25 duplicates the read target data stored in the first storage area 23 as hot data to the newly assigned second storage area address of the second storage area 24. Then, the storage control unit 25 updates the address control table. Then, the memory control unit 25 advances the process to step S38.

On the other hand, in step S37, the storage control unit 25 acquires the data to be read from the second storage area 24. The storage control unit 25 may temporarily store the data to be read in the buffer memory 210 shown in FIG. Then, the memory control unit 25 advances the process to step S38.

In step S38, the storage control unit 25 outputs the data to be read to the host device 4 via the communication unit 21.

Further, in step S39, the storage control unit 25 stores the data to be read in the second storage area 24 in the same manner as in step S33 according to the determination that the control mode is the second mode (No in step S32). Determine if it has been done. If the storage control unit 25 determines that the data to be read is stored in the second storage area 24 (Yes in step S39), the process proceeds to step S41, and if not (No in step S39), the process is performed. Proceed to step S40.

In step S40, the storage control unit 25 acquires the data to be read from the first storage area 23, as in step S34. Then, the memory control unit 25 advances the process to step S42.

Further, in step S41, the storage control unit 25 acquires the data to be read from the second storage area 24 as in step S37. Then, the memory control unit 25 advances the process to step S42.

Then, in step S42, the storage control unit 25 outputs the data to be read to the host device 4 via the communication unit 21 in the same manner as in step S38.

As described above, in the first mode, the storage control unit 25 copies the hot data to the second storage area 24 in response to the detection of the hot data from the first data stored in the first storage area 23. Remember. Then, in the first mode, the storage control unit 25 preferentially outputs the data to be read from the second storage area 24 in response to receiving the data read request. As a result, the storage device 2 can make the second storage area 24 function as a read cache of the first storage area 23, and can speed up the read process. In the second embodiment, the storage control unit 25 can preferentially output the read target data from the second storage area 24 even in the second mode to speed up the read process.

FIG. 12 is a diagram schematically showing a storage state at an arbitrary time point in the first mode of the first storage area 23 and the second storage area 24 according to the second embodiment.

Here, as shown in FIG. 12, in the first storage area 23 of the storage unit 22, the first storage area addresses "A001", "A002", and "A003" have "Data-1" and "Data-2", respectively. "And" Data-3 "data are stored. Here, "Data-1" of the first storage area address "A001" is hot data whose read frequency is equal to or higher than the second threshold value at the time of reading, and is "Data-2" of "A002" and "Data-1" of "A003". -3 ”is assumed to be cold data whose read frequency is less than the second threshold value at the time of reading. In this case, the hot data "Data-1" is duplicated in the second storage area address "B001" of the second storage area 24 by the read process, and the cold data is not duplicated in the second storage area 24.

The storage control unit 25 refers to the read frequency management table of the data usage status monitoring unit 28, and reassigns the second storage area address to the data in the second storage area 24 based on the data read frequency. good. As an example, the storage control unit 25 may reassign the second storage area address in descending order of read frequency.
This process may be performed at any time in the first mode. Further, this process may be performed at any time even in the second mode.

As described above, according to the second embodiment, the second storage area 24, which functions as a cache of the first storage area 23, also functions as a storage destination of data for ensuring reliability when the cumulative write amount is exceeded. .. Therefore, the storage device 2 can improve the processing performance and prevent the deterioration of data reliability with a simple configuration. As a result, the cost of the storage device 2 can be reduced.
The data usage status monitoring unit 28 and the cumulative write amount monitoring unit 29 can be easily implemented by diverting general-purpose functions.

<Embodiment 3>
Next, Embodiment 3 of the present disclosure will be described with reference to FIGS. 13 to 14. The third embodiment is characterized in that the storage device corrects the data to be more reliable when a read error occurs.
FIG. 13 is a block diagram showing an example of the configuration of the storage device 3 according to the third embodiment together with the host device 4. The storage device 3 according to the third embodiment has basically the same configuration and function as the storage device 2 according to the second embodiment. However, the storage device 3 according to the third embodiment is different from the storage device 2 according to the second embodiment in that the storage control unit 35 is provided in place of the storage control unit 25.

The memory control unit 35 has a correction unit 36 in addition to the configuration and function of the memory control unit 25.
When the read target data is stored in the second storage area 24 in response to the occurrence of a read error in response to the data read request in the second mode, the correction unit 36 stores the read target data in the second storage area 24. Get from. Then, the correction unit 36 outputs the read target data to the host device 4 via the communication unit 21.

FIG. 14 is a flowchart showing an example of read processing in the second mode of the storage device 3 according to the third embodiment. The storage device 3 executes the read process shown in steps S50 to 57 instead of steps S39 to 42 in FIGS. 10 to 11 in response to the request for read.

First, in step S50, when the storage control unit 35 determines in step S32 shown in FIG. 10 that the control mode is the second mode (No in step S32), the storage control unit 35 reads the data to be read from the first storage area 23 and acquires the data. do. The storage control unit 35 temporarily stores the acquired data in the buffer memory 210 shown in FIG.

Next, in step S51, the storage control unit 35 determines whether or not a read error has occurred. If the storage control unit 35 determines that a read error has occurred (Yes in step S51), the process proceeds to step S52, and if not (No in step S51), the process proceeds to step S57.

In step S52, the correction unit 36 of the storage control unit 35 discards the read target data acquired from the first storage area 23 from the buffer memory 210.

Then, in step S53, the correction unit 36 of the storage control unit 35 uses the address control table to determine whether or not the data to be read is stored in the second storage area 24. If the correction unit 36 determines that the data to be read is stored in the second storage area 24 (Yes in step S53), the process proceeds to step S54, and if not (No in step S53), the process is stepped. Proceed to S56.

In step S54, the correction unit 36 of the storage control unit 35 reads and acquires the data to be read from the second storage area 24. The correction unit 36 of the storage control unit 35 temporarily stores the acquired data in the buffer memory 210.

Next, in step S55, the correction unit 36 of the storage control unit 35 determines whether or not a reading error has occurred. If the correction unit 36 determines that a read error has occurred (Yes in step S55), the process proceeds to step S56, and if not (No in step S55), the process proceeds to step S57.

In step S56, the correction unit 36 of the storage control unit 35 discards the read target data acquired from the second storage area 24 from the buffer memory 210, and indicates that a data error has occurred in the host device 4 via the communication unit 21. Notice.

On the other hand, in step S57, the storage control unit 35 outputs the data to be read to the host device 4 via the communication unit 21.

As described above, according to the third embodiment, the storage device 3 outputs the data stored in the second storage area 24 with less deterioration when a read error occurs in the second mode. As a result, the second storage area can ensure the reliability of the data when the cumulative write amount is exceeded.

The present disclosure is not limited to the above embodiment, and can be appropriately modified without departing from the spirit.

Further, in the above-described embodiment, the present disclosure has been described as a hardware configuration, but the present disclosure is not limited thereto. The present disclosure can also be realized by causing a processor to execute a computer program. As the processor, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an FPGA (Field-Programmable Gate Array), a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), or the like may be used. Further, a plurality of these may be used in parallel.

In the above example, the program can be stored and supplied to the computer using various types of non-transitory computer readable medium. Non-temporary computer-readable media include various types of tangible storage media. Examples of non-temporary computer-readable media include magnetic recording media (eg, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (eg, magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs. Includes CD-R / W, DVD (Digital Versatile Disc), semiconductor memory (eg, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (Random Access Memory)). The program may also be supplied to the computer by various types of transient computer readable medium. Examples of temporary computer readable media include electrical, optical, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

1,2,3 storage system (storage device)
4 Host device 12,22 Storage unit 13,23 First storage area 14,24 Second storage area 15,25,35 Storage control unit 21 Communication unit 27 Monitoring unit 28 Data usage status monitoring unit 29 Cumulative write amount monitoring unit 36 Correction unit 200 Interface 205 Interface controller 210 Buffer memory 230 1st storage element group 240 2nd storage element group 270 Storage element control unit 280 Data usage status monitoring unit 290 Storage element usage status monitoring unit

Claims (10)

A storage unit having a first storage area for storing the first data and a second storage area for storing the second data, and a storage unit.
The first storage area and the second storage area are provided with a storage control unit that controls reading and writing of data according to a mode.
The memory control unit
In the first mode in which the cumulative write amount of the first storage area is less than the predetermined first threshold value, the hot data in which the number of reads within the predetermined time is equal to or more than the predetermined second threshold value is obtained from the first data. Depending on what is detected, a copy of the hot data is stored in the second storage area.
In the second mode in which the cumulative write amount of the first storage area is equal to or greater than the first threshold value, the data related to the write request is transferred to the first storage area in response to the receipt of the data write request to the first storage area. 2 Store in the storage area
In the second mode, when the data related to the read request is stored in the second storage area in response to the occurrence of a read error for the data read request, the data related to the read request is stored in the second storage area. Output from storage area
Storage system. A storage unit having a first storage area for storing the first data and a second storage area for storing the second data, and a storage unit.
A storage control unit that controls reading and writing of data to the first storage area and the second storage area according to a mode.
Equipped with
The memory control unit
In the first mode in which the cumulative write amount of the first storage area is less than the predetermined first threshold value, the hot data in which the number of reads within the predetermined time is equal to or more than the predetermined second threshold value is obtained from the first data. Depending on what is detected, a copy of the hot data is stored in the second storage area.
When the cumulative write amount of the first storage area changes from the first mode to the second mode in which the cumulative write amount of the first storage area is equal to or greater than the first threshold value, the data storage destination for the data write request to the first storage area is set. Add the second storage area
Storage system. In the first mode or the second mode, the storage control unit preferentially outputs the data related to the read request from the second storage area in response to receiving the data read request.
The storage system according to claim 2. The storage system according to any one of claims 1 to 3, wherein the first storage area and the second storage area are storage areas that are logically distinguished from each other. In the second mode, the storage control unit sends the data related to the write request to the first storage area and the second storage area in response to receiving the data write request to the first storage area. The storage system according to any one of claims 1 to 4 to be stored. Any of claims 1 to 5, wherein the storage control unit selectively erases the data stored in the second storage area in the second mode based on the writing time or the number of readings within a predetermined time. The storage system described in one item. A data usage monitoring unit that monitors the usage status of data stored in the first storage area, and a data usage monitoring unit.
The storage system according to any one of claims 1 to 6, further comprising a cumulative write amount monitoring unit that monitors the cumulative write amount of the storage element of the storage unit. When the cumulative write amount of the first storage area of the storage unit is less than the predetermined first threshold value, the mode is set to the first mode, and the mode is set to the first mode.
When the cumulative write amount of the first storage area of the storage unit is equal to or greater than the first threshold value, the mode is set to the second mode.
In the first mode, the hot data in which the number of times of reading within a predetermined time is equal to or more than a predetermined second threshold value is detected from the first data stored in the first storage area. Data duplication is stored in the second storage area of the storage unit,
In the second mode, in response to receiving a request to write data to the first storage area, the data related to the write request is stored in the second storage area .
In the second mode, when the data related to the read request is stored in the second storage area in response to the occurrence of a read error for the data read request, the data related to the read request is stored in the second storage area. Output from storage area
Storage control method. When the cumulative write amount of the first storage area of the storage unit is less than the predetermined first threshold value, the mode is set to the first mode, and the mode is set to the first mode.
When the cumulative write amount of the first storage area of the storage unit is equal to or greater than the first threshold value, the mode is set to the second mode.
In the first mode, the hot data in which the number of times of reading within a predetermined time is equal to or more than a predetermined second threshold value is detected from the first data stored in the first storage area. Data duplication is stored in the second storage area of the storage unit,
When the mode is changed from the first mode to the second mode, the second storage area is added to the storage destination of the data related to the request for writing the data to the first storage area.
Storage control method. A storage control program that causes a computer to execute the storage control method according to claim 8 or 9.

Images