JP2010160654A - Cache memory backup device, method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce capacity of a backup power supply by reducing a time spent for saving data stored in a cache memory when supply of power from a main power supply stops, and to facilitate maintenance of the backup power supply. <P>SOLUTION: A cache memory backup device 50 includes: a volatile cache memory 54; a nonvolatile memory 54 for evacuating the data stored in the cache memory, having capacity not less than the cache memory; and a capacitor 51 supplying power to the cache memory and the nonvolatile memory when the supply of the power from the main power supply to the cache memory stops. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cache memory backup device, method and program, and more particularly to a cache memory backup device, method and program in a storage system.

  In the storage system, a cache memory that temporarily records data is used in order to speed up the writing of data from the host to the storage. When the cache memory is a volatile memory, it is necessary to prevent the data recorded in the cache memory from being lost when the supply of power from the main power supply to the cache memory is stopped.

Conventionally, when the supply of power from the main power supply is stopped,
(1) The data on the cache memory is retained by the backup power supply.
(2) Switch to power supply using a backup power supply and write the data in the cache memory to the original location.
(3) Processing such as switching to power supply by a backup power source and writing data on the cache memory to a save-only area (disk medium or the like) is performed.

  Note that Patent Document 1 describes a storage system that can reduce the capacity of a battery required for backup of a volatile cache memory. Further, Patent Document 2 describes an electronic device that stores data to be backed up when an abnormality occurs in a power supply, and has a configuration that is not complicated and can be sufficiently downsized.

JP 2008-108026 A JP 2008-140233 A

  The following analysis was made by the present inventors.

When the data on the cache memory is held by the backup power source as in (1) above,
(A) It is necessary to retain data until power is restored so that the data is not lost.
(B) Because it is necessary to consider the time until power recovery,
There was a problem that a large-capacity backup power source (for example, a battery) was required.

On the other hand, as in (2) and (3) above, when writing data on the cache memory to another device,
(A) Writing data to a storage having a structure such as a database is often random access, and data and control information in the cache memory are constantly updated at the time of access, so writing to other devices is not possible. It becomes continuous writing,
(B) In order to efficiently write data to other devices, complicated control such as rearrangement of write data and write order is required,
(C) The cache control unit (write data size, cache page size, etc.) does not always match the save-only area or storage control unit (flash ROM block size, RAID striping size, etc.). Because it is necessary to read the missing data to match the control unit,
There is a problem that it takes time to control writing to other devices and a large-capacity backup power source (for example, a battery) is required.

  The storage system described in Patent Document 1 also needs to include a battery as a secondary power source. As the battery for the backup power source, for example, a lead storage battery, a nickel metal hydride battery, a lithium ion battery, or the like is used. However, because these batteries have a lifetime, items such as the capacity of the battery to be mounted and the number of charge / discharge cycles need to be examined in detail based on the data retention time in the cache memory and the data write time. There is. Therefore, there is a problem that the maintenance of the backup power source becomes complicated.

  Therefore, the capacity of the backup power supply is reduced by reducing the time required to save the data stored in the cache memory when the power supply from the main power supply is stopped, and the maintenance of the backup power supply is facilitated. Is a problem. An object of the present invention is to provide a cache memory backup device, method and program for solving such a problem.

  A cache memory backup device according to a first aspect of the present invention has a volatile cache memory and a non-volatile memory for saving data stored in the cache memory, having a capacity equal to or greater than that of the cache memory. And a capacitor that supplies power to the cache memory and the nonvolatile memory when the supply of power from the main power supply to the cache memory is stopped.

  The cache memory backup method according to the second aspect of the present invention is a nonvolatile memory having a capacity equal to or greater than that of the cache memory and the cache memory when the supply of power from the main power supply to the volatile cache memory is stopped. The method includes a step of supplying power from the capacitor to the memory, and a step of saving data stored in the cache memory to the nonvolatile memory.

  The cache memory backup program according to the third aspect of the present invention is a non-volatile memory having a capacity equal to or greater than that of the cache memory and the cache memory when the supply of power from the main power supply to the volatile cache memory is stopped. Causes the computer to execute a process of supplying power from the capacitor to the nonvolatile memory and a process of saving the data stored in the cache memory to the nonvolatile memory.

  A storage system according to an embodiment of the present invention includes a storage for storing user data, and the above-described cache memory backup device, and the cache memory temporarily holds the user data and / or Alternatively, it holds control information for storing user data in the storage.

  The cache memory backup program can be recorded on any recording medium.

  According to the cache memory backup device, method, and program of the present invention, the capacity of the backup power supply can be reduced by reducing the time required to save the data stored in the cache memory when the power supply from the main power supply is stopped. And the maintenance of the backup power supply can be facilitated. The reason is as follows.

  When the supply of power from the main power supply stops, the entire area of the cache memory is continuously saved in block units of the nonvolatile memory (for example, flash ROM), thereby efficiently writing to the nonvolatile memory. It can be performed. That is, control such as data rearrangement is unnecessary, saving control can be simplified, and penalties (for example, reading of insufficient data for matching control units) that occur when writing to the nonvolatile memory can be eliminated. it can. Therefore, the time required to save the data stored in the cache memory can be reduced.

  Further, since the time required for saving data is reduced, the capacity of the backup power source can be reduced. Therefore, a capacitor can be used instead of a battery as a backup power source. Therefore, maintenance of the bank up power supply can be facilitated.

1 is a block diagram illustrating a configuration of a cache memory backup device according to an embodiment of the present invention. It is a block diagram which shows the structure of the storage system which concerns on the Example of this invention. It is another block diagram which shows the structure of the storage system based on the Example of this invention. It is a flowchart which shows the outline | summary of operation | movement of the cache memory backup apparatus based on the Example of this invention. 4 is a flowchart showing details of the operation of the cache memory backup device according to the embodiment of the present invention. It is another flowchart which shows the detail of operation | movement of the cache memory backup apparatus based on the Example of this invention. It is another flowchart which shows the detail of operation | movement of the cache memory backup apparatus based on the Example of this invention.

  A cache backup device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the cache backup device 50 according to this embodiment. Referring to FIG. 1, the cache backup device 50 includes a volatile cache memory 53, a nonvolatile memory 54, and a capacitor 51.

  The nonvolatile memory 54 has the same capacity as or larger than that of the cache memory 53 and saves data stored in the cache memory 53. The capacitor 51 supplies power to the cache memory 53 and the nonvolatile memory 54 when the supply of power from the main power supply 40 to the cache memory 53 is stopped.

  Further, the data stored in the cache memory 53 may be saved in units of blocks of the nonvolatile memory 54. Further, the nonvolatile memory 54 may be a flash ROM.

  Further, the cache memory backup device 50 may further include a control unit 52. The control unit 52 monitors the supply of power from the main power supply 40 to the cache memory 53, and supplies power from the capacitor 51 to the cache memory 53 and the nonvolatile memory 54 when the supply of power is stopped. Control.

  Further, the storage system 70 may include a storage 60 for storing user data and the cache memory backup device 50 described above. In this case, the cache memory 53 temporarily holds the user data and / or holds control information for storing the user data in the storage 60. The storage system may further include a main power supply 40.

  Embodiments of the present invention will be described with reference to the drawings.

(Constitution)
FIG. 2 is a block diagram illustrating the configuration of the storage system 80 according to the present embodiment. Referring to FIG. 2, the storage system 80 includes a control board 10 as a cache memory backup device, an external storage device 20 as a storage, and further includes an I / O host 30 and a main power supply 40.

  The control board 10 is powered by the main power supply 40. The control board 10 is connected to the I / O host 30 and the external storage device 20. The control board 10 includes a capacitor 11, a control processor 12, and a volatile cache memory 13, and includes a flash ROM 14 having the same capacity as the cache memory 13 as a nonvolatile memory.

  FIG. 3 is another block diagram illustrating the configuration of the storage system 80 according to the present embodiment. FIG. 3 is a block diagram when the supply of power from the main power supply 40 is stopped. The capacitor 11 operates as a backup power supply when the supply of power from the main power supply 40 is stopped, and the control processor 12 and the cache memory on the control board 10 are at least required for the saving control of the cache memory 13. 13 and the flash ROM 14 are supplied with power.

  When the control processor 12 receives power from the main power supply 40 and receives a write request from the I / O host 30, the control processor 12 temporarily sends control information and write data for writing to the cache memory 13. Record and notify the I / O host 30 of completion to complete the write request. Further, when there is unwritten data on the cache memory 13, the control processor 12 writes the data to the external storage device 20 according to the control information as needed.

  When the supply of power from the main power supply 40 is stopped, the control processor 12 recognizes that the power supply has been switched to the supply of the capacitor 11, and performs all the data on the cache memory 13 as a save process of the cache memory 13. Is copied to the flash ROM 14.

(Operation)
The operation of the cache memory backup device according to this embodiment will be described with reference to the drawings. FIG. 4 is a flowchart showing an outline of the operation of the cache memory backup device according to this embodiment.

  Referring to FIG. 4 and FIG. 5, the control processor 12 always monitors the supply of power from the main power supply 40 (step S10), and when there is power supply from the main power supply 40 (Yes in step S11), Response control to the I / O request from the I / O host 30 (step S20) and write control of unwritten data on the cache memory 13 to the external storage device 20 (step S30) are performed.

  Referring to FIG. 6, the control processor 12 checks the main power supply power supply flag in response control to the I / O request (step S21), and if power supply is being performed (Yes in step S21), It is determined whether or not there is a write request from the host 3 (step S22). When there is a write request (Yes in Step S22), the control processor 12 saves the write address information and the write data on the cache memory 13 (Step S23), and the storage location on the cache memory 13 and the external storage device Unwritten information indicating that writing to 20 has not been performed is added to the control information (step S24), and an end response is returned in response to the write request (step S25).

  Referring to FIG. 7, the control processor 12 checks the main power supply in-progress flag in the unwritten data write control (step S30) (step S31), and if power is being supplied (Yes in step S31), The control information on the cache memory 13 is checked to determine whether or not the external storage device 20 has not been written (step S32). If there is unwritten data (Yes in step S32), the control processor 12 writes the unwritten data to the external storage device 20 (step S33), and stores the unwritten information included in the control information after the writing is completed. Delete (step S34).

  Referring to FIG. 3, when the supply of power from the main power supply 40 is stopped, the control processor 12, the cache memory 13 and the flash ROM 14 are supplied with power from the capacitor 11.

  Referring to FIG. 5, when the control processor 12 detects that the supply of power from the main power supply 40 is stopped (No in step S11), the control control for the I / O request from the I / O host 30 is performed. And, in order to stop the writing control of the unwritten data on the cache memory 13 to the external storage device 20, the main power supply power supply flag is set to stop (step S12). Further, the control processor 12 determines whether there is unwritten data in the external storage device 20 (step S13). When there is unwritten data (Yes in step S13), the control processor 12 saves (copys) the data in the cache memory 13 to the flash ROM 14 in units of blocks of the flash ROM 14, which is the most efficient access unit for the flash ROM 14. (Steps S14 to S17).

(effect)
As described above, according to the cache memory backup device (control board 10) according to the present embodiment, it is possible to reduce the amount of backup power. Therefore, instead of using a battery as a backup power source, a large capacity capacitor can be used.

  In addition, the time required for the cache memory saving process can be shortened. This is because saving control can be executed for each block of the flash ROM by making the cache memory and the saving flash ROM have the same capacity and saving all the data in the cache memory.

  Furthermore, maintenance of the backup power source is facilitated. This is because it is not necessary to perform periodic supplementary charging at the time of storage unlike a battery conventionally used as a backup power source.

  Further, it is not necessary to consider the life of the flash ROM. When unwritten data exists in the cache memory, the cache memory is saved only when power supply from the main power supply is stopped due to an unexpected accident such as a power failure. Therefore, writing to the flash ROM occurs rarely.

  Although the above description has been made based on examples, the present invention is not limited to the above examples.

  As an example, the cache backup device, method, and program according to the present invention are applied to a small-scale storage system using an SSD (Solid State Drive) that can be realized by a small-capacity backup power supply as an external storage device. be able to. The program can be recorded on an arbitrary recording medium.

10 Control board 11, 51 Capacitor 12 Control processor 13, 53 Cache memory 14 Flash ROM
20 External storage device 30 I / O host 40 Main power supply 50 Cache memory backup device 52 Control unit 54 Non-volatile memory 60 Storage 70, 80 Storage system

Claims (12)

Volatile cache memory,
A non-volatile memory having a capacity equal to or greater than that of the cache memory and for saving data stored in the cache memory;
A cache memory backup device comprising: a capacitor for supplying power to the cache memory and the nonvolatile memory when supply of power from a main power supply to the cache memory is stopped.   2. The cache memory backup device according to claim 1, wherein the data stored in the cache memory is saved in units of blocks of the nonvolatile memory.   The cache memory backup device according to claim 1, wherein the nonvolatile memory is a flash ROM.   A control unit that monitors the supply of power from the main power source to the cache memory and controls the cache memory and the nonvolatile memory to supply power from the capacitor when the supply of power is stopped The cache memory backup device according to claim 1, further comprising: Storage to store user data;
A cache memory backup device according to any one of claims 1 to 4,
The storage system, wherein the cache memory temporarily holds the user data and / or holds control information for storing the user data in a storage.   The storage system according to claim 5, further comprising the main power source. Supplying power from a capacitor to the cache memory and a nonvolatile memory having a capacity equal to or greater than that of the cache memory when supply of power from the main power supply to the volatile cache memory is stopped;
And a step of saving the data stored in the cache memory in the nonvolatile memory.   8. The cache memory backup method according to claim 7, wherein the data stored in the cache memory is saved in units of blocks of the nonvolatile memory. Monitoring the supply of power from the main power supply to the cache memory by a control unit;
A step of controlling by the control unit to supply power from the capacitor to the cache memory and the non-volatile memory when the supply of power from the main power supply is stopped, The cache memory backup method according to claim 7 or 8. A process of supplying power from a capacitor to the cache memory and a non-volatile memory having a capacity equal to or greater than the cache memory when the supply of power from the main power supply to the volatile cache memory is stopped;
A cache memory backup program causing a computer to execute a process of saving data stored in the cache memory to the nonvolatile memory.   11. The cache memory backup program according to claim 10, which causes a computer to execute a process of saving data stored in the cache memory in units of blocks of the nonvolatile memory. A process of monitoring the supply of power from the main power supply to the cache memory;
When the supply of power from the main power supply is stopped, the computer is further caused to perform processing for controlling the cache memory and the nonvolatile memory to supply power from the capacitor. Item 12. A cache memory backup program according to Item 10 or 11.

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