Method and apparatus for the takeover of primary volume in multiple volume mirroring

• US 20050034013A1
• Filed: 09/03/2004
• Published: 02/10/2005
• Est. Priority Date: 10/12/2000
• Status: Active Grant

• Current Assignee: Hitachi America Limited (Hitachi, Ltd.)
• Original Assignee: Hitachi America Limited (Hitachi, Ltd.)
• Inventors: Yamamoto, Masayuki, Yamamoto, Akira, Yamagami, Kenji
• Granted Patent: US 7,281,158 B2
• Time in Patent Office: Days
• US Class Current: 714/6
• CPC Class Codes: G06F 11/2058 using more than 2 mirrored copies
• CPC Class Codes: G06F 11/2069 Management of state, configuration or failover

Abstract

A multiple disk system comprises plural physical drives organized as plural groups of disks. Each group is accessed as a plurality of logical volumes. One of the logical drives is considered a primary volume and one or more other logical volumes are considered as secondary volumes, which together constitute a mirroring group. Data contained in a memory records such organization. The data is consulted to select a secondary volume when the disk group containing a primary volume fails.

Claims

1. A disk system comprising:

plural input-output (I/O) ports;

plural disk groups, each disk group configured as a redundant array, each disk group being arranged into one or more logical volumes, each logical volume comprising at least two disk drive units, a first of said logical volumes being a primary volume and one or more others of said logical volumes being secondary volumes; and

a disk controller operatively coupled to each of said I/O ports to receive I/O requests from one or more host systems, said disk controller configured to write data to said primary volume and to one or more of said secondary volumes to satisfy said I/O requests, wherein data that is written to said primary volume is mirrored to said one or more of said secondary volumes,

said disk controller being operable to select one of said secondary volumes in an available disk group as a replacement volume of said primary volume when at least one disk group in said primary volume becomes unavailable.

2. The system of claim 1 wherein said disk controller includes a memory configured to store a first table indicating to which disk group each of said logical volumes belongs and a second table indicating the availability of each disk group.

3. The system of claim 1 wherein each disk group is configured in accordance with level 1 RAID.

4. The system of claim 1 wherein each disk group is configured in accordance with level 5 RAID.

5. The system of claim 1 wherein each disk group is configured in accordance with one of level 1, 2, 3, 4, and 5 RAID architectures.

6. A disk system comprising:

a plurality of input/output (I/O) ports;

a data processing unit in data communication with said I/O ports;

a first disk group and a second disk group, each of which is configured as a redundant array of disk drives, said redundant array of disk drives of said first disk group including a first volume, said redundant array of disk drives of said second disk groups including a second volume; and

a first memory configured to contain first program code executable by said data processing unit to write data to said first volume and to said second volume such that data written to said first volume is mirrored in said second volume.

7. The system of claim 6 wherein said first program code accesses said disk groups in accordance with level 3 or level 5 RAID techniques.

8. The system of claim 6 further comprising a second memory configured to contain second program code executable by said data processing unit to use said second volume as a replacement volume of said first volume when said first volume becomes unavailable.

9. The system of claim 8 further comprising:

a third memory configured to identify said first volume as a first logical volume and said second volume as a second logical volume; and

a fourth memory configured to indicate an availability status of each of said first logical volume and said second logical volume.

10. The system of claim 9 wherein said third and fourth memories are contained in a single memory.

11. The system of claim 9 wherein said fourth memory is configured as a table containing an entry for each disk group, each entry containing an availability status information.

12. A method for data access comprising:

grouping a plurality of disk drives into at least two disk groups, at least one disk group comprising disk drives configured as a redundant array;

organizing each disk group into one or more logical volumes, each said one or more logical volumes comprising two or more disk drives of one of said disk groups, a first logical volume among said disk groups being a primary volume, others of said one or more logical volumes being one or more secondary volumes, wherein data written to said primary volume is also written to said secondary volumes such that data in said primary volume is mirrored in said secondary volumes; and

if said primary volume becomes unavailable, then designating one of said secondary volumes as a failover primary volume, including identifying said disk group to which said primary volume belongs and eliminating secondary volumes located on said disk group as candidates for said failover primary volume, wherein data is subsequently written to said failover primary volume.

13. The method of claim 12 wherein one of said disk groups is not configured as a redundant array.

14. The method of claim 12 wherein said primary volume belongs to a disk group that is configured as a redundant array and said failover primary volume belongs to a disk group that is not configured as a redundant array.

15. The method of claim 12 wherein said primary volume belongs to a disk group that is not configured as a redundant array and said failover primary volume belongs to a disk group that is configured as a redundant array.

16. The method of claim 12 wherein said disk groups are organized in accordance with one of level 1, 2, 3, 4, or 5 RAID techniques.

17. The method of claim 12 wherein said organizing includes creating first information that identifies to which disk group each of said logical volumes belongs, wherein said designating is based on said first information.

18. The method of claim 12 further including splitting one or more of said secondary volumes to produce one or more split volumes, said designating further including eliminating said split volumes as candidates for said failover primary volume.

19. The method of claim 12 wherein said primary volume is unavailable if at least one of its disk drives is unavailable.

20. The method of claim 12 further including receiving a maintenance request to make a first disk group unavailable, wherein said primary volume is unavailable if at least one of its disk drives belongs to said first disk group.