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

• US 6,810,491 B1
• Filed: 10/12/2000
• Issued: 10/26/2004
• Est. Priority Date: 10/12/2000
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi America Limited (Hitachi, Ltd.)
• Inventors: Yamamoto, Masayuki, Yamagami, Kenji, Yamamoto, Akira
• Primary Examiner(s): Iqbal, Nadeem
• Assistant Examiner(s): Bonura, Timothy M.
• Application Number:
  US09/687,059
• Time in Patent Office: 1,475 Days
• Field of Search: 714/6, 714/7, 714/42
• US Class Current: 714/6.11
• 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 multiple disk system having a failover component, the system comprising:

plural input-output (I/O) ports;

plural disk groups, each disk group comprising plural disk drive units, each disk group being arranged into one or more logical volumes, each logical volume comprising at least two of said 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;

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 read and write data to said primary volume and to copy said data 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; and

a detector operable with said disk controller to detect when a disk group has become unavailable, said detector further configured to determine whether an unavailable disk group includes said primary volume and if so to select one of said secondary volumes as a replacement volume, said replacement volume being in an available disk group.

2. The system of claim 1 wherein said detector 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 2 wherein said detector is a component of said disk controller.

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

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

6. 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.

7. 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 plurality of disk groups, each comprising a plurality of disk drives;

a first memory configured to identify a plurality of logical volumes, each logical volume comprising two or more disk drives from one of said disk groups, one of said logical volumes being a primary volume, others of said logical volumes being a plurality of secondary volumes;

a second memory configured to indicate an availability status of each of said disk groups;

a third memory configured to contain first program code executable by said data processing unit to access said disk groups to write data to said primary volume and to said secondary volumes such that data written to said primary volume is mirrored in said secondary volumes; and

a fourth memory configured to contain second program code executable by said data processing unit to select one of said secondary volumes as a backup primary volume upon detecting that the disk group to which said primary volume belongs has an unavailable status by inspecting said first and second memories.

8. The system of claim 7 wherein said first and second memories are contained in a single memory store.

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

10. The system of claim 7 wherein said second memory is configured as a table containing an entry for each disk group, each entry containing an availability status information.

11. A method for data access comprising:

grouping a plurality of disk drives into one or more disk groups, each disk group comprising one or more of said disk drives;

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;

detecting unavailability of said primary volume; and

in response to said detecting, 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.

12. The method of claim 11 wherein said logical volumes are organized in accordance with level 3 or level 5 RAID techniques.

13. The method of claim 11 wherein said organizing includes creating first information which identifies to which disk group each of said logical volumes belongs, wherein said designating is based on said first information.

14. The method of claim 11 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.

15. The method of claim 11 further including maintaining first information indicative of the availability of each of said disk groups, wherein said detecting includes detecting unavailability of one of said disk groups and determining whether said primary volume belongs to said one of said disk groups.

16. The method of claim 15 further including detecting a failed disk drive and in response thereto modifying said first information to indicate that the disk group associated with said failed disk drive is unavailable.

17. The method of claim 15 further including receiving a maintenance request to make one of said disk groups unavailable and in response thereto modifying said first information to indicate that said one of said disk groups is unavailable.