System and method for raid management, reallocation, and restriping

• US 7,886,111 B2
• Filed: 05/24/2007
• Issued: 02/08/2011
• Est. Priority Date: 05/24/2006
• Status: Active Grant

• Current Assignee: Dell International LLC (Dell Technologies Inc.)
• Original Assignee: Compellent Technologies Incorporated (Dell Technologies Inc.)
• Inventors: Uttormark, Michael J., Klemm, Michael J.
• Primary Examiner(s): Kim; Matt
• Assistant Examiner(s): Verderamo, III; Ralph A
• Application Number:
  US11/753,364
• Publication Number:
  US 20080109601A1
• Time in Patent Office: 1,356 Days
• Field of Search: None
• US Class Current: 711/114
• CPC Class Codes: G06F 2211/1004 Adaptive RAID, i.e. RAID system adapts to changing circumstances, e.g. RAID1 becomes RAID5 as disks fill up
• CPC Class Codes: G06F 3/0607 by facilitating the process of upgrading existing storage systems, e.g. for improving compatibility between host and storage device
• CPC Class Codes: G06F 3/0608 Saving storage space on storage systems
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/0632 by initialisation or re-initialisation of storage systems
• CPC Class Codes: G06F 3/0647 Migration mechanisms
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD

Abstract

The present disclosure relates to systems and methods for RAID Restriping. One method includes selecting an initial RAID device for migration based on at least one score, creating an alternate RAID device, moving data from the initial RAID device to the alternate RAID device, and removing the initial RAID device. The method may be performed automatically by the system or manually. The method may be performed periodically, continuously, after every RAID device migration, upon addition of disk drives, and/or before removal of disk drives, etc. One system includes a RAID subsystem and a disk manager configured to automatically calculate a score for each RAID device, select a RAID device based on the relative scores of the RAID devices, create an alternate RAID device, move data from the selected RAID device to the alternate RAID device, and remove the selected RAID device.

Claims

1. A method of RAID restriping in a disk drive system, comprising:

selecting a RAID device for migration from a plurality of RAID devices based on a comparison between an initial score and at least one second score calculated for each of the plurality of RAID devices, wherein;

the initial score relates to the RAID device in its present state and is calculated based on one or more scoring factors; and

the second score relates to at least one hypothetical RAID device located in available disk space and is calculated based on one or more scoring factors;

creating at least one alternate RAID device based on the at least one hypothetical RAID device;

moving data stored at the selected RAID device to the at least one alternate RAID device; and

removing the selected RAID device.

2. The method of claim 1, wherein the at least one second score comprises a replacement score relating to at least one hypothetical RAID device located in existing available disk space.

3. The method of claim 1, wherein the at least one second score comprises an overlay score relating to at least one hypothetical RAID device located in a combination of existing available disk space and at least a portion of the disk space taken up by the RAID device.

4. The method of claim 1, wherein the one of one or more scoring factors comprise one or more of the RAID level, RAID stripe size, RAID extent size, disk category, location on disk, disk enclosure, disk enclosure power supply, and communication path to the disk.

5. The method of claim 4, wherein the factors have varying weights for use in the calculation.

6. The method of claim 4, wherein selecting a RAID device for migration based on a comparison between an initial score and at least one second score calculated for each of a plurality of RAID devices comprises selecting the RAID device if the least one second score is better than the initial score.

7. The method of claim 1, wherein the initial score and the at least one second score are each calculated using the same scoring factors.

8. The method of claim 1, wherein the steps of selecting a RAID device for migration, creating at least one alternate RAID device, moving data, and removing the selected RAID device are done automatically without manual intervention.

9. The method of claim 8, wherein the steps are performed without loss of server data access to the disk drive system and compromised resiliency of the data.

10. The method of claim 8, wherein the steps are performed at least one of periodically, continuously, after every RAID device migration, upon addition of disk drives, and before removal of disk drives.

11. The method of claim 1, wherein the steps of selecting a RAID device for migration, creating at least one alternate RAID device, moving data, and removing the selected RAID device are done manually.

12. The method of claim 1, wherein moving data stored at the selected RAID device to the at least one alternate RAID device further comprises creating at least one temporary RAID device.

13. The method of claim 12, further comprising moving data stored at the selected RAID device to the at least one temporary RAID device and then from the temporary RAID device to the at least one alternate RAID device.

14. A disk drive system, comprising:

a RAID subsystem; and

a disk manager having at least one disk storage system controller configured to automatically;

select a RAID device from the plurality of RAID devices based on a comparison between an initial score and at least one second score calculated for the plurality of RAID devices, wherein the initial score relates to the RAID device in its present state and is calculated based on one or more scoring factors and the second score relates to at least one hypothetical RAID device located in available disk space and is calculated based on one or more scoring factors;

create an alternate RAID device based on the at least one hypothetical RAID device;

move at least a portion of the data stored at the selected RAID device to the alternate RAID device; and

remove the selected RAID device.

15. The disk drive system of claim 14, wherein the at least one second score comprises an overlay score related to at least one second hypothetical RAID device located in a combination of existing available disk space and at least a portion of the disk space taken up by the RAID device.

16. The disk drive system of claim 15, wherein the at least one second alternate RAID device is based on one of the first and second hypothetical RAID devices.

17. The disk drive system of claim 14, wherein the disk drive system comprises storage space from at least one of a plurality of RAID levels including RAID-0, RAID-1, RAID-5, and RAID-10.

18. The system of claim 17, further comprising RAID levels including RAID-3, RAID-4, RAID-6, and RAID-7.