High availability cache in server cluster

• US 9,952,949 B2
• Filed: 11/20/2015
• Issued: 04/24/2018
• Est. Priority Date: 01/20/2014
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Chiu, Lawrence Y., Liu, Yang, Muench, Paul H., Toohey, Timothy L.
• Primary Examiner(s): CHU, GABRIEL L
• Application Number:
  US14/948,013
• Publication Number:
  US 20160077932A1
• Time in Patent Office: 886 Days
• CPC Class Codes: G06F 11/1658 Data re-synchronization of a redundant component, or initial sync of replacement, additional or spare unit
• CPC Class Codes: G06F 11/2033 switching over of hardware resources
• CPC Class Codes: G06F 11/2038 with a single idle spare processing component
• CPC Class Codes: G06F 11/2043 where the redundant components share a common memory address space
• CPC Class Codes: G06F 11/2046 where the redundant components share persistent storage G06F11/2043 takes precedence
• CPC Class Codes: G06F 11/2094 Redundant storage or storage space G06F11/2056 takes precedence
• CPC Class Codes: G06F 12/0817 using directory methods
• CPC Class Codes: G06F 12/0828 with concurrent directory accessing, i.e. handling multiple concurrent coherency transactions
• CPC Class Codes: G06F 12/121 using replacement algorithms
• CPC Class Codes: G06F 2201/885 Monitoring specific for caches
• CPC Class Codes: G06F 2211/1009 Cache, i.e. caches used in RAID system with parity
• CPC Class Codes: G06F 2212/621 Coherency control relating to peripheral accessing, e.g. from DMA or I/O device
• CPC Class Codes: H04L 67/568 Storing data temporarily at an intermediate stage, e.g. caching

Abstract

For a high availability cache, a cache module obtains permission to manage the cache in response to a failover event in a server cluster by communicating a cache coherency token. An update module rebuilds a cache directory from data stored in the cache and accesses the cache without reloading the data stored in the cache.

Claims

1. An apparatus comprising:

a processor;

a computer readable storage medium that stores program code executable by the processor to;

obtain permission for an active cache coherency manager to manage a cache in response to a failover event by communicating a cache coherency token to the active cache coherency manager, wherein a plurality of cache coherency managers accesses the cache; and

rebuild a cache directory using the active cache coherency manager from data stored in the cache and access the cache without reloading the data stored in the cache.

2. The apparatus of claim 1, wherein the failover event is in a server cluster that comprises a primary server, a secondary server, a primary storage system, and a secondary storage system, the primary server accesses data from the primary storage system, the cache caches primary storage system data, and the secondary storage system is synchronized with the primary storage system.

3. The apparatus of claim 2, wherein the processor further:

receives the cache coherency token at a first cache manager of the primary server; and

shares the cache coherency token with a second cache manager of the secondary server.

4. The apparatus of claim 2, wherein the failover event is a failover from the primary server to the secondary server.

5. The apparatus of claim 2, wherein the failover event is a failover from the primary storage system to the secondary storage system.

6. The apparatus of claim 2, wherein the processor further halts input/output to cached volumes in the primary storage system and resumes input/output to cached volumes in one of the primary storage system and the secondary storage system.

7. The apparatus of claim 1, wherein rebuilding the cache directory comprises replacing a primary storage system volume identifier with a secondary storage system volume identifier for each cache line.

8. A method for a high availability cache comprising:

obtaining, by use of a processor, permission for an active cache coherency manager to manage a cache in response to a failover event by communicating a cache coherency token to the active cache coherency manager, wherein a plurality of cache coherency managers accesses the cache;

rebuilding a cache directory using the active chache coherency manager from data stored in the cache; and

accessing the cache without reloading the data stored in the cache.

9. The method of claim 8, wherein the failover event is in a server cluster that comprises a primary server, a secondary server, a primary storage system, and a secondary storage system, the primary server accesses data from the primary storage system, the cache caches primary storage system data, and the secondary storage system is synchronized with the primary storage system.

10. The method of claim 9, the method further comprising:

receiving the cache coherency token at a first cache manager of the primary server; and

sharing the cache coherency token with a second cache manager of the secondary server.

11. The method of claim 9, wherein the failover event is a failover from the primary server to the secondary server.

12. The method of claim 9, wherein the failover event is a failover from the primary storage system to the secondary storage system.

13. The method of claim 9, the method further comprising:

halting input/output to cached volumes in the primary storage system; and

resuming input/output to cached volumes in one of the primary storage system and the secondary storage system.

14. The method of claim 8, wherein rebuilding the cache directory comprises replacing a primary storage system volume identifier with a secondary storage system volume identifier for each cache line.

15. A computer program product for a high availability cache, the computer program product comprising a non-transitory computer readable storage medium having program code embodied therein, the program code readable/executable by a processor to:

obtain permission for an active cache coherency manager to manage a cache in response to a failover event by communicating a cache coherency token to the active cache coherency manager, wherein a plurality of cache coherency managers accesses the cache;

rebuild a cache directory using the active cache coherency manager from data stored in the cache; and

access the cache without reloading the data stored in the cache.

16. The computer program product of claim 15, wherein the failover event is in a server cluster that comprises a primary server, a secondary server, a primary storage system, and a secondary storage system, the primary server accesses data from the primary storage system, the cache caches primary storage system data, and the secondary storage system is synchronized with the primary storage system.

17. The computer program product of claim 16, the program code further:

receiving the cache coherency token at a first cache manager of the primary server; and

sharing the cache coherency token with a second cache manager of the secondary server.

18. The computer program product of claim 16, wherein the failover event is a failover from the primary server to the secondary server.

19. The computer program product of claim 16, wherein the failover event is a failover from the primary storage system to the secondary storage system.

20. The computer program product of claim 16, the program code further:

halting input/output to cached volumes in the primary storage system; and

resuming input/output to cached volumes in one of the primary storage system and the secondary storage system.