Storage device, storage system, and backup method

Abstract

To provide a storage apparatus capable of suppressing a decrease in backup processing speed.SOLUTION: A storage apparatus comprises an information management unit, a data management unit, a determination unit, and a transmission control unit. The information management unit acquires mapping information from the backup destination storage apparatus. The data management unit manages whether or not data have been updated since the last backup on a block-by-block basis. The determination unit determines whether the blocks are continuous in the backup destination storage apparatus based on the mapping information. The transmission control unit transmits a write instruction to a storage medium at the backup destination if the blocks are continuous at the backup destination. The transmission control unit transmits the write instruction to an extended cache memory if the blocks are not continuous at the backup destination.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a storage device, a storage system, and a backup method. [Background technology]

[0002] Block storage, which stores data in blocks, reduces the amount of data transfer by transferring updated blocks of data when backing up data to other storage. The backup destination storage stores the transferred data in cache memory and writes the data from the cache memory to a storage medium, thereby backing up the transferred data. In such a storage system, if the amount of data transferred for backup increases, the write process may become a rate-limiting factor in the case of a slow storage medium, and the backup processing speed may decrease. In particular, if the blocks on the backup destination storage medium are not contiguous, the processing speed decreases significantly. For example, Patent Document 1 discloses a technology for reducing the decrease in processing speed when backing up data between block storages.

[0003] The storage system of Patent Document 1 writes data directly to a storage medium when the blocks to which data is written are consecutive in a backup destination storage device. Also, when the blocks are not consecutive, the storage system of Patent Document 1 writes the data to a high-speed storage medium first, and then writes the data to the storage medium. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-041471 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the storage system described in Patent Document 1 may not be able to determine the continuity of blocks if a thin provisioning function is used in the backup destination storage device.

[0006] An object of the present invention is to provide a storage device or the like that can suppress a decrease in the backup processing speed. [Means for solving the problem]

[0007] In order to solve the above problems, the storage device of the present invention comprises an information management means for managing mapping information obtained from the backup destination storage device, a data management means for managing whether data in the storage area has been updated since the previous backup on a block-by-block basis, a determination means for determining based on the mapping information whether the backup destination of the data of the updated block is a consecutive block in the backup destination storage device, and a transmission control means for controlling the transmission of an instruction to write to the backup destination storage medium and the backup data to the backup destination storage device if the backup destination is a consecutive block, and for controlling the transmission of an instruction to write to the extended cache memory and the backup data to the backup destination storage device if the backup destination is a distant block.

[0008] The backup method of the present invention manages mapping information obtained from the backup destination storage device, manages whether data in the storage area has been updated since the previous backup on a block-by-block basis, determines based on the mapping information whether the backup destination for the data in the updated block is a consecutive block in the backup destination storage device, and if the block is a consecutive block, controls to send an instruction to write to the backup destination block and the backup data to the backup destination storage device, and if the block is a distant block, controls to send an instruction to write to the extended cache memory and the backup data to the backup destination storage device. [Effects of the Invention]

[0009] According to the present invention, it is possible to suppress a decrease in the backup processing speed. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating an outline of the configuration of a first exemplary embodiment of the present invention. [Figure 2] FIG. 1 illustrates an example of a configuration of a storage apparatus according to a first embodiment of the present invention. [Figure 3] 3 shows an example of a differential bitmap according to the first embodiment of the present invention. [Figure 4] FIG. 1 illustrates an example of a configuration of a storage apparatus according to a first embodiment of the present invention. [Figure 5] FIG. 3 is a diagram illustrating an example of mapping information according to the first exemplary embodiment of the present invention. [Figure 6] FIG. 4 is a diagram illustrating an example of an operation flow of the storage device according to the first embodiment of the present invention. [Figure 7] FIG. 4 is a diagram illustrating an example of an operation flow of the storage device according to the first embodiment of the present invention. [Figure 8] FIG. 4 is a diagram illustrating an example of an operation flow of the storage device according to the first embodiment of the present invention. [Figure 9] FIG. 10 is a diagram illustrating an outline of the configuration of a second exemplary embodiment of the present invention. [Figure 10] FIG. 10 is a diagram illustrating an example of an operation flow of a storage device according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] (First embodiment) A first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an outline of the configuration of an information processing system of this embodiment. The information processing system includes a server 10, a storage device 20, and a storage device 30. The storage device 20 is a backup source storage device when backing up data in the information processing system. The storage device 30 is a backup destination storage device when backing up data in the information processing system. The server 10 and the storage device 20 are connected via a network. The storage device 20 and the storage device 30 are also connected via a network.

[0012] In the information processing system of this embodiment, the storage device 20 and the storage device 30 each manage their storage areas in block units. The server 10 writes data to the storage device 20 and reads data from the storage device 20. The storage device 20 backs up the stored data to the storage device 30 using a replication function. The storage device 20 stores data, in block units, that manages whether data has been updated since the previous backup, as a differential bitmap. The storage device 20 reduces the amount of data transfer by transferring only the data of the updated blocks to the storage device 30 as backup data.

[0013] The storage device 30, which is the data backup destination, has a thin provisioning function. The thin provisioning function is a technology that virtualizes the storage capacity of a storage device. With the thin provisioning function, a virtual volume is allocated when a request to secure an area is made, and a physical area is allocated when actual writing is performed.

[0014] The server 10 is an information processing device that performs processing according to the application. The server 10 reads data required for processing executed on the server 10 from the storage device 20. The server 10 also writes data generated by the execution of the processing into the storage device 20.

[0015] The following describes the configuration of the storage device 20. Fig. 2 is a diagram showing an example of the configuration of the storage device 20. The storage device 20 includes a control unit 21, an acquisition unit 22, a data transmission unit 23, and a storage medium 100.

[0016] The control unit 21 manages the storage area of the storage medium 100 and controls the backup of data stored in the storage medium 100 to the storage device 30. The control unit 21 further includes a data management unit 24, an information management unit 25, an information storage unit 26, a determination unit 27, and a transmission control unit 28.

[0017] The data management unit 24 manages for each block whether data has been updated since the previous backup was performed. The data management unit 24 holds data indicating whether each block has been updated as a differential bitmap. The differential bitmap is a data table that divides the storage area into blocks and indicates for each block whether data has been updated since the previous backup was performed.

[0018] Figure 3 is a diagram that shows a schematic image of a differential bitmap. A differential bitmap is a table that divides a storage area into blocks. The differential bitmap stores "1" for blocks that have been updated and "0" for blocks that have not been updated. The blocks are arranged in order according to the area of the logical volume to be backed up. A logical volume is a unit for dividing storage area in block storage. From the information in the differential bitmap, the amount of data difference since the previous backup can be obtained as the number of blocks that have been updated. Furthermore, from the information in the differential bitmap, information on the blocks that will be the target of the next backup can be obtained.

[0019] The information management unit 25 manages mapping information of the storage device 30. The data management unit 24 acquires mapping information of the thin provisioning function from the storage device 30 via the acquisition unit 22. The mapping information is information that associates logical volumes with physical areas of the storage medium allocated to each logical volume.

[0020] The information management unit 25 manages a data table showing the correspondence between each block of the storage medium 100 and the backup destination block in the storage device 30. The information management unit 25 generates a data table by associating each block of the storage medium 100 with the backup destination block in the storage device 30 based on mapping information. The backup destination block in the storage device 30 is notified to the storage device 20 from the storage device 30 using a logical volume when data is backed up for the first time.

[0021] The information storage unit 26 stores data necessary for data backup processing. The information storage unit 26 stores a differential bitmap, mapping information, and a data table showing the correspondence between each block of the storage medium 100 and the backup destination block in the storage device 30.

[0022] The determination unit 27 determines whether the blocks on the storage device 30, which is the backup destination of the data, are consecutive. The determination unit 27 determines whether the blocks on the backup destination are consecutive by referring to the mapping information of the thin provisioning function of the backup destination storage device 30, which is acquired by the information management unit 25, and determining whether the blocks on the backup destination are consecutive.

[0023] The transmission control unit 28 uses the replication function of the block storage to control the backup of data to the storage device 30 by asynchronous differential copying. The transmission control unit 28 references the differential bitmap and transfers data of blocks that have been updated since the previous backup was performed to the storage device 30 as backup data. The backup data is data that is to be backed up when backing up data from the storage device 20, which is the backup source, to the storage device 30, which is the backup destination.

[0024] The transmission control unit 28 determines the write destination of the data to be backed up based on the determination result of the determination unit 27. If the determination result shows that the blocks of the backup destination are contiguous, the transmission control unit 28 controls the data transmission unit 23 and the storage medium 100 to send an instruction to write the data to the storage medium and the backup data to the backup destination storage device 30. If the determination result shows that the blocks of the backup destination are not contiguous, that is, if the blocks of the backup destination are separated, the transmission control unit 28 controls the data transmission unit 23 and the storage medium 100 to send an instruction to write to the extended cache memory and the backup data to the storage device 30.

[0025] The acquiring unit 22 acquires data used for each process in the storage device 20. The acquiring unit 22 acquires a request to write data and data to be written from the server 10. The acquiring unit 22 acquires a request to read data from the server 10. The acquiring unit 22 also acquires mapping information of the storage device 30 from the storage device 30.

[0026] The data transmission unit 23 transmits information about the data write destination and the backup data to the storage device 30. The data transmission unit 23 transmits to the server 10 the data for which a read request has been made.

[0027] The processes in the data management unit 24, information management unit 25, determination unit 27, transmission control unit 28, acquisition unit 22, and data transmission unit 23 of the control unit 21 are performed, for example, by executing a computer program on a CPU (Central Processing Unit). The processes in the data management unit 24, information management unit 25, determination unit 27, transmission control unit 28, acquisition unit 22, and data transmission unit 23 of the control unit 21 may be performed, for example, by a semiconductor device such as an FPGA (Field Programmable Gate Array). The information storage unit 26 is configured, for example, using a non-volatile semiconductor storage device.

[0028] The storage medium 100 is configured using, for example, a hard disk drive. However, the storage medium 100 is not limited to a hard disk drive. The storage medium 100 may be configured with multiple hard disk drives. Furthermore, the storage medium 100 may be provided in a housing separate from the storage device 20, as long as it is configured to be controlled by the storage device 20.

[0029] The following describes the configuration of the storage device 30. Fig. 4 is a diagram showing an example of the configuration of the storage device 30. The storage device 30 includes a control unit 31, an output unit 32, a data receiving unit 33, a storage medium 110, and an extended cache memory 120. The storage device 30 is a storage device that manages storage areas using a thin provisioning function.

[0030] The control unit 31 manages the storage area of the storage medium 110. It also controls writing of data to the storage medium 110 and the extended cache memory 120, and writing of data stored in the extended cache memory to the storage device 30. The control unit 31 further includes an area management unit 34, a mapping information storage unit 35, and a write control unit 36.

[0031] The area management unit 34 manages data stored in the storage medium 110 for each block. The area management unit 34 manages the storage area using a thin provisioning function. The area management unit 34 sends mapping information to the storage device 20 via the output unit 32.

[0032] FIG. 5 shows an example of mapping information used by the area management unit 34 to manage storage areas. The mapping information is composed of a logical volume number, a logical volume block number, a disk number, and a disk block number. The logical volume number is an identification number for each logical volume. The logical volume block number is an identification number for each block within the logical volume. The disk number and disk block number are the identification numbers for the disk and the block within the disk corresponding to each block in the logical volume. In storage devices that use the thin provisioning function, logical volume data is often distributed across multiple storage media. Therefore, the area management unit 34 uses mapping information such as that shown in FIG. 5 to associate and manage logical volumes with corresponding storage media.

[0033] The mapping information storage unit 35 stores the mapping information.

[0034] The write control unit 36 controls writing of data to the extended cache memory 120 and the storage medium 110. When a command to write data to the extended cache memory is issued, the write control unit 36 controls writing of data received from the storage device 20 to the extended cache memory 120 via the data receiving unit 33. Furthermore, when the access frequency to the storage medium 110 is equal to or lower than a reference value, the write control unit 36 controls writing of data written to the extended cache memory 120 to the storage medium 110. The reference value for the access frequency is set appropriately using, for example, the number of accesses to the storage medium 110 per unit time. When data from the extended cache memory 120 is written to the storage medium 110, the write control unit 36 erases the backup data that has been written to the storage medium 110 from the extended cache memory 120. When a command to write data to the storage medium is issued, the write control unit 36 controls writing of the received backup data to the storage medium 110 via the data receiving unit 33.

[0035] The output unit 32 sends the mapping information to the storage device 20. When a request to read data is made, the output unit 32 outputs the specified data on the storage medium 110 to the storage device 20 or the server 10.

[0036] The data receiving unit 33 receives a data write request, a data write destination, and backup data from the storage device 20. The data receiving unit 33 receives a mapping information request from the storage device 20.

[0037] The processes in the area management unit 34 of the control unit 31, the write control unit 36, the output unit 32, and the data receiving unit 33 are performed, for example, by executing a computer program on a CPU. The processes in the area management unit 34, the write control unit 36, the output unit 32, and the data receiving unit 33 may be performed, for example, by a semiconductor device such as an FPGA. The mapping information storage unit is configured, for example, using a non-volatile semiconductor storage device.

[0038] The storage medium 110 is configured using, for example, a hard disk drive. The storage medium 110 may be configured with multiple hard disk drives. Furthermore, the storage medium 110 may be provided in a housing separate from the storage device 30, as long as it is configured to be controlled by the storage device 30.

[0039] The extended cache memory 120 is configured using, for example, a non-volatile semiconductor memory device.

[0040] The operation of the information processing system of this embodiment will be described.

[0041] First, we will explain the operation when the server 10 writes data to the storage medium 100 of the storage device 20. The server 10 sends a data write instruction and the data to be written to the storage device 20. Upon receiving the write instruction, the data management unit 24 controls the storage medium 100 so that the received data is written to the storage medium 100.

[0042] When data is written to the storage medium 100, the data management unit 24 updates the differential bitmap information stored in the information storage unit 26 for the block to which the data has been written. The data management unit 24 updates the data of the block to which the data has been written to "1".

[0043] Next, a description will be given of the operation of the storage device 20 to acquire mapping information from the storage device 30. Fig. 6 is a diagram showing an example of the operation flow when the storage device 20 acquires mapping information.

[0044] The information management unit 25 checks whether a predetermined time has passed since the previous acquisition of mapping information. The predetermined time is set in advance based on, for example, the update frequency of mapping information in the storage device 30. If the predetermined time has not passed since the previous acquisition of mapping information (No in step S11), the information management unit 25 waits until the predetermined time has passed. If the predetermined time has passed since the previous acquisition of mapping information (Yes in step S11), the information management unit 25 acquires mapping information from the storage device 30 via the acquisition unit 22 (step S12). After acquiring the mapping information, the information management unit 25 updates the mapping information stored in the information storage unit 26 with the acquired data (step S13).

[0045] Next, a process in which the storage device 20 backs up data stored in the storage medium 100 to the storage device 30 will be described. Fig. 7 is a diagram showing an example of the operation flow of the storage device 20 when backing up data from the storage device 20 to the storage device 30. Fig. 8 is a diagram showing an example of the operation flow of the storage device 30 when backing up data from the storage device 20 to the storage device 30.

[0046] The transmission control unit 28 refers to the differential bitmap stored by the information management unit 25 at predetermined time intervals to check whether data on the storage medium 100 has been updated. The predetermined time, which is the time interval for checking whether data has been updated, is set appropriately based on, for example, the amount or frequency of data stored from the server 10 to the storage device 20. If there are no updated blocks (No in step S21), the transmission control unit 28 waits until the predetermined time has elapsed again.

[0047] If the data has been updated (Yes in step S21), the determination unit 27 refers to the map information and determines whether the blocks at the backup destination are consecutive (step S22). After determining whether the blocks at the backup destination are consecutive, the determination unit 27 checks whether there are any other blocks where data has been updated. If there are any other blocks where data has been updated (Yes in step S23), the determination unit 27 performs the process of step S22 on the blocks where data has been updated.

[0048] If there are no other updated blocks (No in step S23), the transmission control unit 28 starts the process of transmitting the backup data.

[0049] If the determination result by the determination unit 27 indicates that the blocks to be backed up are consecutive (Yes in step S24), the transmission control unit 28 controls the data transmission unit 23 and the storage medium 100 to send an instruction to write to the storage medium and to transmit the backup data to the storage device 30 via the data transmission unit 23 (step S25).

[0050] If the determination result by the determination unit 27 shows that the blocks of the backup destination are not consecutive (No in step S24), the transmission control unit 28 controls the data transmission unit 23 and the storage medium 100 to send an instruction to write to the extended cache memory and to transmit the backup data to the storage device 30 via the data transmission unit 23 (step S26). When the blocks of the backup destination are not consecutive, that is, when the blocks that are to be the backup destination in the storage device 30 are far apart.

[0051] After transmitting the backup data, the transmission control unit 28 checks whether there are any blocks among the updated blocks that have not been transmitted. If there are any blocks that have not been transmitted (Yes in step S27), the transmission control unit 28 repeats the operations from step S24. If all the data of the updated blocks has been transmitted (No in step S27), the storage device 20 waits until it is time to perform the next backup process. The next backup process may be performed when a preset time has elapsed since the previous backup was performed, for example. The storage device 20 may also perform the backup process when it receives a backup instruction from the server 10.

[0052] The write control unit 36 of the storage device 30 receives an instruction for the data write destination and backup data from the storage device 20 via the data receiving unit 33 (step S31). Upon receiving the instruction for the data write destination, the write control unit 36 checks whether the instruction for the data write destination is the extended cache memory 120 or the storage medium 110.

[0053] If the instruction to write the data to the storage medium is Yes in step S32, the write control unit 36 controls the storage medium 110 so that the received backup data is written to the specified block, and writes the backup data received from the storage device 20 to the storage medium 110 (step S38). After writing the backup data to the storage medium 110 is complete, the write control unit 36 checks whether there is any backup data that has not been written. If there is any backup data that has not been written (Yes in step S39), the write control unit 36 repeats the operations from step S32. If there is no backup data that has not been written (No in step S39), the write control unit 36 waits until the next backup instruction is sent.

[0054] If the instruction to write the data to the extended cache memory 120 is given (No in step S32), the write control unit 36 controls the extended cache memory 120 to write the received backup data to the extended cache memory 120 (step S33).

[0055] The write control unit 36 checks the operating state of the storage medium 110 and checks the frequency of access to the storage medium. If the access frequency is higher than the standard (No in step S35), the write control unit 36 continues to monitor the access frequency until the access frequency falls below the standard.

[0056] If the access frequency is equal to or lower than the reference value (Yes in step S35), the write control unit 36 controls the extended cache memory 120 and the storage medium 110 to write the data in the extended cache memory 120 to the storage medium 110 (step S36).

[0057] When writing of the backup data in the extended cache memory 120 to the storage medium 110 is complete, the write control unit 36 erases the backup data that has been written to the storage medium 110 from the extended cache memory 120. After erasing the backup data, the write control unit 36 checks whether the extended cache memory 120 contains backup data that has not yet been written to the storage medium 110. If there is backup data that has not yet been written (Yes in step S37), the write control unit 36 repeats the operations from step S35. If there is no data that has not yet been written (No in step S37), the write control unit 36 waits until the next backup instruction is sent.

[0058] The backup source storage device 20 acquires mapping information for the backup destination storage device 30 and selects either the extended cache memory 120 or the storage medium 110 as the data write destination depending on whether the backup destination blocks are contiguous. However, for example, suppose the mapping status of the backup destination is unknown, and all data is written to the backup destination cache memory and then written from the cache memory to the storage medium. In such a case, if the amount of data to be backed up increases, the cache memory of the copy destination storage device may run out of free space during processing. When the cache memory runs out of free space, data must be frequently written from the cache memory to the storage medium to ensure free space in the cache memory. This places a high load on the write destination storage medium and may result in a decrease in processing speed. Furthermore, if the cache memory continues to run out of free space, a delay occurs in the transmission of backup data from the backup source storage device to the backup destination storage device, which may result in the system not meeting the backup time specifications. In particular, if the backup destination storage medium is slow, a high load state is likely to persist, potentially lengthening the backup time.

[0059] In such a configuration, the backup source storage device 20 of the information processing system of this embodiment acquires mapping information from the backup destination storage device 30 using the thin provisioning function and determines whether the backup destination blocks are blocks separated from consecutive blocks. If the write destination blocks are consecutive, the backup source storage device 20 sends an instruction to the backup destination storage device 30 to write data directly to the storage medium, thereby reducing the load on the storage medium caused by writing data from the extended cache memory to the storage medium. In this way, by using the mapping information acquired from the backup destination to determine whether the backup destination blocks are consecutive and selecting the data write destination to reduce the load on the storage medium, the information processing system of this embodiment can prevent a decrease in backup processing speed.

[0060] (Second embodiment) A second embodiment of the present invention will be described in detail with reference to the drawings. Fig. 9 is a diagram showing an outline of the configuration of a storage device 200 of this embodiment. The storage device 200 of this embodiment includes an information management unit 201, a data management unit 202, a determination unit 203, and a transmission control unit 204.

[0061] The information management unit 201 acquires mapping information from the backup destination storage device. The data management unit 202 manages, on a block-by-block basis, whether data in the storage area has been updated since the previous backup. The determination unit 203 determines, based on the mapping information, whether the backup destination of the updated block data is a contiguous block in the backup destination storage device. If the backup destination is a contiguous block, the transmission control unit 204 controls the transmission of an instruction to write to the backup destination storage medium and the backup data to the backup destination storage device. If the backup destination is a distant block, the transmission control unit 204 controls the transmission of an instruction to write to the extended cache memory and the backup data to the backup destination storage device.

[0062] The operation of the storage device 200 of this embodiment will be described below. Fig. 10 is a diagram showing an example of the operation flow of the storage device 200.

[0063] The information management unit 201 acquires mapping information from the backup destination storage device (step S201). The data management unit 202 manages whether data in the storage area has been updated since the time of backup on a block-by-block basis (step S202). The determination unit 203 determines, based on the mapping information, whether the backup destination of the data of the updated block is a consecutive block in the backup destination storage device (step S203). If the backup destination is a consecutive block (Yes in step S204), the transmission control unit 204 controls to send an instruction to write to the backup destination storage medium and the backup data to the backup destination storage device (step S205). If the backup destination is a distant block (No in step S204), the transmission control unit 204 controls to send an instruction to write to the extended cache memory and the backup data to the backup destination storage device (step S206).

[0064] The storage device 200 of this embodiment acquires mapping information from the backup destination storage device and determines whether the backup destination blocks are blocks separated from consecutive blocks. When the write destination blocks are consecutive, data is written directly to the storage medium, thereby reducing the load on the storage medium caused by writing data from the cache memory to the storage medium and preventing a decrease in the backup processing speed. [Explanation of symbols]

[0065] 10 Servers 20 Storage Devices 21 Control Unit 22 Acquisition Department 23 Data transmission unit 24 Data Management Department 25 Information Management Department 26 Information storage section 27 Judgment section 28 Transmission control section 30 Storage Devices 31 Control Unit 32 Output section 33 Data receiving unit 34 Area Management Department 35 Mapping information storage unit 36 Write control section 100 storage medium 110 Storage medium 120 Extended Cache Memory 200 storage devices 201 Information Management Department 202 Data Management Department 203 Judgment section 204 Transmission control section

Claims

1. an information management means for managing mapping information acquired from the backup destination storage device; a data management means for managing whether or not data has been updated since the previous backup in units of blocks in the storage area; a determining means for determining whether the backup destination of the updated block data is a continuous block in the backup destination storage device based on the mapping information; a transmission control means for controlling the transmission of an instruction to write to a storage medium of the backup destination and the backup data to the storage device of the backup destination when the backup destination is a continuous block, and for controlling the transmission of an instruction to write to an extended cache memory and the backup data to the storage device of the backup destination when the backup destination is a separate block; Equipped with Storage device.

2. the information management means manages each block of the storage area and a backup destination block in the backup destination storage device by associating them with each other based on the mapping information; The storage device according to claim 1 .

3. the data management means checks whether the data has been updated since the previous backup when a preset time has elapsed since the previous backup.

3. The storage device according to claim 1.

4. the data management means manages whether or not each block has been updated since the previous backup as a differential bitmap; 4. The storage device according to claim 1.

5. an output means for transmitting mapping information of the storage area to the storage device that is the source of the backup data; a data receiving means for receiving, from the source storage device, backup data and information indicating whether the backup data is to be written to an extended cache memory or a storage medium; a write control means for controlling, when the information indicates that the backup data is to be written to the extended cache memory, to hold the received backup data in the extended cache memory and then write the received backup data from the extended cache memory to the storage medium, and, when the information indicates that the backup data is to be written to the storage medium, to write the received backup data to the storage medium; A storage device comprising:

6. the write control means controls the backup data stored in the extended cache memory to be written to the storage medium when the access frequency to the storage medium is equal to or lower than a predetermined standard, and controls the backup data stored in the extended cache memory to be erased after writing to the storage medium has been completed. The storage device according to claim 5 .

7. a first storage device comprising the storage device according to any one of claims 1 to 4; a second storage device comprising the storage device according to claim 5 or 6; Equipped with the information management means of the first storage device manages the mapping information acquired from the second storage device; the transmission control means of the first storage device transmits a write destination instruction and the backup data to the second storage device; the write control means of the second storage device stores the backup data based on the instruction of the write destination. Storage system.

8. Manages mapping information acquired from the backup destination storage device, The system manages whether data has been updated since the last backup in the storage area on a block-by-block basis, determining whether the backup destination of the updated block data is a continuous block in the backup destination storage device based on the mapping information; If the blocks are consecutive, control is performed so that an instruction to write to the backup destination block and the backup data are sent to the backup destination storage device, and if the blocks are distant, control is performed so that an instruction to write to the extended cache memory and the backup data are sent to the backup destination storage device. Backup method.

9. Each block of the storage area is managed in association with a backup destination block in the backup destination storage device based on the mapping information. The backup method according to claim 8.

10. Sending mapping information of the storage area to the storage device that is the source of the backup data; receiving, from the source storage device, backup data and information indicating whether the backup data is to be written to an extended cache memory or a storage medium; When the information indicates that the backup data is to be written to the extended cache memory, the received backup data is stored in the extended cache memory and then written from the extended cache memory to the storage medium, and when the information indicates that the backup data is to be written to the storage medium, the received backup data is written to the storage medium. Backup method.

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