Repairing a site cache in a distributed file system

• US 10,423,507 B1
• Filed: 12/22/2015
• Issued: 09/24/2019
• Est. Priority Date: 12/05/2014
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Inventors: Panghal, Vijay, Quah, Kee Shen, Javadekar, Shrinand
• Primary Examiner(s): Choe, Yong J
• Application Number:
  US14/978,424
• Time in Patent Office: 1,372 Days
• CPC Class Codes: G06F 11/2069 Management of state, configuration or failover
• CPC Class Codes: G06F 11/2082 Data synchronisation
• CPC Class Codes: G06F 16/172 Caching, prefetching or hoarding of files
• CPC Class Codes: G06F 16/182 Distributed file systems
• CPC Class Codes: G06F 16/183 Provision of network file services by network file servers, e.g. by using NFS, CIFS network file access protocols H04L67/1097
• CPC Class Codes: G06F 2201/885 Monitoring specific for caches
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/0683 Plurality of storage devices
• CPC Class Codes: H04L 67/1097 for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS]
• CPC Class Codes: H04L 67/568 Storing data temporarily at an intermediate stage, e.g. caching

Abstract

A failing computer readable storage medium comprising a portion of a transient object store is detected at a site cache. The site cache associated with the transient object store is set to an error read only state. The failing computer readable storage medium is replaced with an operational computer readable storage medium.

Claims

1. A method for repairing a site cache, the method comprising:

detecting a failing computer readable storage medium comprising a portion of a transient object store;

setting a site cache associated with the transient object store to an error read only state in which the site cache does not service write requests, wherein the error read only state supersedes a read only state of the site cache and supersedes a read write state of the site cache;

after the site cache has been set to the error read only state, replacing the failing computer readable storage medium with an operational computer readable storage medium; and

changing the site cache from the error read only state.

2. The method of claim 1, further comprising:

receiving a write request at the site cache from a client while the site cache is in the error read only state; and

transmitting the write request from the site cache to an authoritative object store without processing the write request on the site cache.

3. The method of claim 1, further comprising transmitting the error read only state from the site cache to a metadata server (“

MDS”

), wherein the MDS is associated with the site cache.

4. The method of claim 1, further comprising:

receiving a read request or a write request at the site cache from a client; and

detecting the failing computer readable storage medium while processing the read request or the write request on the site cache.

5. The method of claim 4, further comprising scanning a log for a failed disk identifier in response to detecting the failing computer readable storage medium.

6. The method of claim 1, further comprising replicating data objects from a replication computer readable storage medium to the operational computer readable storage medium.

7. The method of claim 6, wherein the data objects were stored on the failing computer readable storage medium.

8. The method of claim 6, further comprising determining the data objects are replicated to the operational computer readable storage medium prior to changing the site cache from the error read only state.

9. A system for repairing a site cache in a distributed file system (“

DFS”

), the system comprising a non-transitory computer readable storage medium and a processor configured to execute instructions for;

detecting a failing computer readable storage medium comprising a portion of a transient object store;

setting a site cache associated with the transient object store to an error read only state in which the site cache does not service write requests, wherein the error read only state supersedes a read only state of the site cache and supersedes a read write state of the site cache;

after the site cache has been set to the error read only state, replacing the failing computer readable storage medium with an operational computer readable storage medium; and

changing the site cache from the error read only state.

10. The system of claim 9, further comprising replicating data objects from a replication computer readable storage medium to the operational computer readable storage medium.

11. The system of claim 10, wherein the data objects were stored on the failing computer readable storage medium.

12. The system of claim 10, further comprising determining the data objects are replicated to the operational computer readable storage medium prior to changing the site cache from the error read only state.

13. A non-transitory computer readable storage medium comprising processor instructions for repairing a site cache in a distributed file system (“

DFS”

), instructions comprising;

detecting a failing computer readable storage medium comprising a portion of a transient object store;

setting a site cache associated with the transient object store to an error read only state in which the site cache does not service write requests, wherein the error read only state supersedes a read only state of the site cache and supersedes a read write state of the site cache;

after the site cache has been set to the error read only state, replacing the failing computer readable storage medium with an operational computer readable storage medium; and

changing the site cache from the error read only state.

14. The non-transitory computer readable storage medium of claim 13, further comprising replicating data objects from a replication computer readable storage medium to the operational computer readable storage medium.

15. The non-transitory computer readable storage medium of claim 14, wherein the data objects were stored on the failing computer readable storage medium.

16. The non-transitory computer readable storage medium of claim 14, further comprising determining the data objects are replicated to the operational computer readable storage medium prior to changing the site cache from the error read only state.

17. The non-transitory computer readable storage medium of claim 13, wherein the instructions further comprise receiving one or both of a read request or write request, and completing the requested operation or operations notwithstanding the detection of the failing computer readable storage medium.

18. The non-transitory computer readable storage medium of claim 13, wherein changing the site cache from the error read only state comprises changing the site cache to a read-only state, or to a read-write state.