SYSTEM AND METHOD FOR RAID MANAGEMENT, REALLOCATION, AND RESTRIPING

• US 20080109601A1
• Filed: 05/24/2007
• Published: 05/08/2008
• 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, Klemm, Michael
• Granted Patent: US 7,886,111 B2
• Time in Patent Office: Days
• 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 the steps of:

selecting a RAID device for migration based on at least one score calculated for each of a plurality of RAID devices;

creating at least one alternate 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 score comprises an initial score and a replacement score, wherein the initial score relates to the RAID device and the replacement score relates to at least one first hypothetical RAID device located in available disk space.

3. The method of claim 2, wherein the at least one score further comprises an overlay score relating to at least one second hypothetical RAID device located in a combination of available disk space and the disk space taken up by the RAID device.

4. The method of claim 3, wherein the initial score, replacement score, and overlay score are each calculated based on at least one of factors comprising 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 5, wherein the initial score, replacement score, and overlay score are each calculated using the same factors.

7. The method of claim 4, wherein selecting a RAID device for migration based on at least one score calculated for each of a plurality of RAID devices comprises selecting the RAID device if at least one of the replacement score or overlay score is better than the initial score.

8. The method of claim 7, wherein the alternate RAID device is based on one of the first and second hypothetical RAID devices.

9. 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.

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

11. The method of claim 9, 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.

12. 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.

13. 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.

14. The method of claim 13, 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.

15. A disk drive system, comprising:

a RAID subsystem; and

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

calculate at least one score for each RAID device of a plurality of RAID devices of the RAID subsystem;

select a RAID device from the plurality of RAID devices based on the relative at least one scores of the plurality of RAID devices.

create an alternate 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.

16. The disk drive system of claim 15, wherein the at least one score comprises an initial score for the RAID device, a replacement score related to a first hypothetical RAID device, and an overlay score related to a second hypothetical RAID device.

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

18. The disk drive system of claim 15, 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.

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

20. A disk drive system capable of RAID restriping, comprising:

means for selecting a RAID device for migration based on at least one score calculated for each of a plurality of RAID devices;

means for creating at least one alternate RAID device;

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

means for removing the selected RAID device.

21. A method for reallocating data, comprising:

determining a score for a current position of data and a score for an alternate position the data;

comparing the score for the current position of the data and the score for the alternate position of the data; and

moving the data from the current position to the alternate position when the score for the alternate position of the data is better than the score for the current position of the data.