Disk array system and rebuild method thereof

• US 20060206753A1
• Filed: 03/08/2006
• Published: 09/14/2006
• Est. Priority Date: 03/10/2005
• Status: Active Grant

• Current Assignee: Cloud BYTE LLC
• Original Assignee: NEC Corporation
• Inventors: Kajiki, Yoshihiro, Yamato, Junichi
• Granted Patent: US 7,739,544 B2
• Time in Patent Office: Days
• US Class Current: 714/6
• CPC Class Codes: G06F 11/1092 Rebuilding, e.g. when physically replacing a failing disk
• CPC Class Codes: G06F 11/1456 Hardware arrangements for backup
• CPC Class Codes: G06F 11/1458 Management of the backup or restore process

Abstract

Disclosed is a disk array system which includes a plurality of disks constituting a disk array and a backup storage for backing up data in the disk array and performs control so that when a failed disk among the disks constituting the disk array is replaced with the replacement disk, restoration of data in the replacement disk is performed using the backup device.

Claims

1. A disk array system comprising:

a plurality of disk drives constituting a disk array;

a backup storage device;

a backup module for performing control so that data in said disk array is backed up onto said backup storage device; and

a rebuild module for performing rebuilding of data in a replacement disk drive, with which a failed disk drive among said disk drives constituting said disk array is replaced, based on the data backed up in said backup storage device.

2. The disk array system according to claim 1, further comprising a modify map for recording information corresponding to an update location, when the data in said disk array is updated.

3. The disk array system according to claim 2, wherein, when the data in said disk array is updated by an access from a host after the backup onto said backup storage device, said backup module sends to said backup storage device the data updated after the backup onto said backup storage device, said modify map records the information corresponding to the updated data;

and said data updated after backup is stored as the backup data in said backup storage device.

4. The disk array system according to claim 3, wherein said rebuild module reads from said backup storage device data stored in said failed disk drive and backed up in said backup storage device, writes the data to said replacement disk drive;

and

after the completion of writing of the data in said failed disk drive to said replacement disk drive from said backup storage device, said rebuild module refers to said modify map, and generates data for said failed disk drive which have been updated after the backup, based on the data on other disk drives constituting said disk array, to write the generated data to said replacement disk drive.

5. The disk array system according to claim 2, wherein said modify map has an update flag corresponding to a unit region for access in each of said disk drives in said disk array, the update flag indicating whether the unit region has been updated or not after the backup.

6. The disk array system according to claim 5, wherein said modify map has a rebuild flag corresponding to the unit region for access in said each of said disk drives in said disk array, the rebuild flag indicating whether rebuilding of the unit region has been performed or not.

7. The disk array system according to claim 6, wherein said rebuild module refers to said modify map after the completion of writing of the data in said failed disk drive to said replacement disk drive from said backup storage device, and generates data on the unit region with the update flag indicating updating and with the rebuild flag indicating that the rebuilding has not been performed yet, based on the data in other disk drives constituting said disk array, to write the generated data to said replacement disk drive.

8. The disk array system according to claim 2, wherein said rebuild module refers to said modify map, and performs control so that writing back from said backup storage device to said replacement disk drive is not performed on a unit region of the failed disk drive updated after the backup.

9. The disk array system according to claim 1, wherein an update to the failed disk during rebuilding of the replacement disk is written to the replacement disk drive without alteration.

10. The disk array system according to claim 1, wherein, even before the rebuilding is finished, when an access request is made to latest data among the data in said replacement disk drive under the rebuilding, access to said replacement disk drive is permitted.

11. The disk array system according to claim 1, further comprising:

a RAID module for performing a normal read/write access to said disk array; and

a disk access bus/switch for data transfer between said backup storage device and said replacement disk drive;

wherein the rebuilding of said replacement disk drive from said backup storage is performed through said rebuild module provided in parallel with said RAID module and said disk access bus/switch, thereby the rebuilding of said replacement disk drive being prohibited from influencing a normal access by said RAID module said to said disk array.

12. A method of rebuilding a disk array system, said method comprising:

backing up data in a disk array including a plurality of disk drives onto a backup storage device; and

performing control so that when a failed disk drive among said disk drives constituting said disk array is replaced with a replacement disk drive, restoration of data in said replacement disk drive is performed by said backup storage device.

13. The method according to claim 12, further comprising:

recording information corresponding to an update location, when the data in said disk array is updated by an access from a host after the backup onto said backup storage device;

sending only the updated data to said backup storage device after the backup onto said backup storage device; and

storing the updated data in said backup storage device as the backup data.

14. The method according to claim 13, further comprising:

reading from said backup storage device data stored in said failed disk drive and backed up in said backup storage device, and writing the data to said replacement disk drive; and

referring to said modify map, after writing of the data in said failed disk drive to said replacement disk drive from said backup storage device is finished, generating data on said failed disk drive updated after the backup, based on the data on other disk drives constituting said disk array and writing the generated data to said replacement disk drive.

15. The method according to claim 13, wherein said modify map has an update flag corresponding to a unit region for access in each of said disk drives in said disk array, the update flag indicating whether the unit region has been updated or not after the backup.

16. The method according to claim 15, wherein said modify map has a rebuild flag corresponding to the unit region for access in said each of said disk drives in said disk array, the rebuild flag indicating whether rebuilding of the unit region has been performed or not.

17. The method according to claim 16, further comprising:

referring to said modify map, after writing of the data in said failed disk drive to said replacement disk drive from said backup storage device is finished;

generating data on the unit region with the update flag indicating updating and with the rebuild flag indicating that the rebuilding has not been performed yet, based on the data in other disk drives constituting said disk array; and

writing the generated data to said replacement disk drive.

18. The method according to claim 12, further comprising

referring to said modify map and performing control so that writing back from said backup storage device is not performed on a unit region of the failed disk drive updated after the backup.

19. The method according to claim 12, further comprising

performing control so that a content updated during the rebuilding of said replacement disk drive is written to said replacement disk drive without using said backup storage device.

20. The method according to claim 12, further comprising

performing control so that even before the rebuilding is finished, when an access request is made to latest data among the data in said replacement disk drive under rebuilding, access to said replacement disk drive is permitted.