Granted Patent B1

US 9,311,242 · App. 13/743,904 · Granted Apr 12, 2016

Inventor: Anindya Banerjee (West Bengal, IN)

Assignee: Symantec Corporation

G06F12/0815G06F3/065G06F11/1402G06F12/0804

Abstract

Claims (87)

1. A computer-implemented method for enabling write-back-cache aware snapshot creation, at least a portion of the method being performed by a computing device comprising at least one processor, the method comprising:

identifying a cache that implements write-back caching to selectively store at least one write to a backing store;

receiving, while the write is stored within the cache, a request to create a snapshot of the backing store, where the write is to be included in the snapshot of the backing store;

creating, in response to the request and while the write is still stored within the cache, the snapshot of the backing store by:

determining that the write is stored within the cache;

tracking the write while the write is still stored within the cache and while the snapshot is accessible to ensure that the write is included in the snapshot of the backing store;

providing read access to the snapshot without first flushing the write to the backing store by receiving, while the write is stored within the cache, a request to read from the snapshot;

satisfying the request to read from the snapshot.

2. The method of claim 1 , wherein:

the write to the backing store is destined for a block of the backing store;

tracking the write while the write is still stored within the cache comprises tracking the block of the backing store to which the write is destined.

3. The method of claim 2 , wherein providing read access to the snapshot without first flushing the write to the backing store further comprises:

detecting a subsequent write to the backing store;

determining, in response to the detection, that the subsequent write to the backing store is destined for the block of the backing store;

flushing, in response to the determination that the subsequent write to the backing store is destined for the block of the backing store, the write from the cache to the snapshot of the backing store.

4. The method of claim 2 , wherein providing read access to the snapshot without first flushing the write to the backing store comprises:

detecting a subsequent request to read from a block of the snapshot;

determining that the block of the snapshot is associated with the block of the backing store;

flushing, prior to satisfying the request to read from the block of the snapshot, the write from the cache to the snapshot of the backing store.

5. The method of claim 2 , wherein providing read access to the snapshot without first flushing the write to the backing store comprises:

detecting a subsequent request to read from a block of the snapshot;

determining that the block of the snapshot is associated with the block of the backing store;

satisfying, while the write is stored within the cache, the request to read from the block of the snapshot with the write stored within the cache.

6. The method of claim 1 , wherein:

tracking the write while the write is still stored within the cache comprises detecting a request to flush the write from the cache to the backing store;

providing read access to the snapshot without first flushing the write to the backing store further comprises flushing, in response to the detection, the write from the cache to the snapshot of the backing store.

7. The method of claim 1 , wherein tracking the write while the write is still stored within the cache comprises:

identifying a cache abstraction layer that manages the cache;

causing the cache abstraction layer to flush the write from the cache to the snapshot of the backing store.

8. The method of claim 7 , wherein causing the cache abstraction layer to flush the write from the cache to the snapshot of the backing store comprises:

identifying a log used by the cache abstraction layer to manage writes stored within the cache;

adding a marker to the log that indicates that the write should be flushed from the cache to the snapshot of the backing store.

9. The method of claim 1 , wherein:

the write to the backing store is destined for a block of the backing store;

tracking the write while the write is still stored within the cache comprises:

maintaining a list of cached blocks of the backing store that includes blocks of the backing store that are cached; and

using the list of cached blocks of the backing store to ensure that the writes stored within the cache and associated with the blocks of the backing store that are cached are included in the snapshot of the backing store.

10. The method of claim 9 , wherein tracking the write while the write is still stored within the cache further comprises:

detecting that the write is no longer stored within the cache;

updating the list of cached blocks of the backing store to reflect that the write is no longer stored within the cache.

11. A system for enabling write-back-cache aware snapshot creation, the system comprising:

a cache-identifying module programmed to identify a cache that implements write-back caching to selectively store at least one write to a backing store;

a request-receiving module programmed to receive, while the write is stored within the cache, a request to create a snapshot of the backing store, where the write is to be included in the snapshot of the backing store;

a snapshot-creating module programmed to:

create, in response to the request and while the write is still stored within the cache, the snapshot of the backing store by:

determining that the write is stored within the cache;

tracking, the write while the write is still stored within the cache and while the snapshot is accessible to ensure that the write is included in the snapshot of the backing store;

provide read access to the snapshot without first flushing the write to the backing store by receiving, while the write is stored within the cache, a request to read from the snapshot;

satisfy the request to read from the snapshot;

at least one processor configured to execute the cache-identifying module, the request-receiving module, and the snapshot-creating module.

12. The system of claim 11 , wherein:

the write to the backing store is destined for a block of the backing store;

the snapshot-creating module is programmed to track the write stored within the cache by tracking the block of the backing store to which the write is destined.

13. The system of claim 12 , wherein the snapshot-creating module is further programmed to provide read access to the snapshot without first flushing the write to the backing store by:

detecting a subsequent write to the backing store;

determining, in response to the detection, that the subsequent write to the backing store is destined for the block of the backing store;

flushing, in response to the determination that the subsequent write to the backing store is destined for the block of the backing store, the write from the cache to the snapshot of the backing store.

14. The system of claim 12 , wherein the snapshot-creating module is programmed to provide read access to the snapshot without first flushing the write to the backing store by:

detecting a subsequent request to read from a block of the snapshot;

determining that the block of the snapshot is associated with the block of the backing store;

flushing, prior to satisfying the request to read from the block of the snapshot, the write from the cache to the snapshot of the backing store.

15. The system of claim 12 , wherein the snapshot-creating module is programmed to provide read access to the snapshot without first flushing the write to the backing store by:

detecting a subsequent request to read from a block of the snapshot;

determining that the block of the snapshot is associated with the block of the backing store;

satisfying, while the write is stored within the cache, the request to read from the block of the snapshot with the write stored within the cache.

16. The system of claim 11 , wherein the snapshot-creating module is programmed to:

track the write stored within the cache by detecting a request to flush the write from the cache to the backing store;

provide read access to the snapshot of the backing store by flushing, in response to the detection, the write from the cache to the snapshot of the backing store.

17. The system of claim 11 , wherein the snapshot-creating module is programmed to track the write while the write is still stored within the cache by:

identifying a cache abstraction layer that manages the cache;

causing the cache abstraction layer to flush the write from the cache to the snapshot of the backing store.

18. The system of claim 17 , wherein the snapshot-creating module is programmed to cause the cache abstraction layer to flush the write from the cache to the snapshot of the backing store by:

identifying a log used by the cache abstraction layer to manage writes stored within the cache;

adding a marker to the log that indicates that the write should be flushed from the cache to the snapshot of the backing store.

19. The system of claim 11 , wherein:

the write to the backing store is destined for a block of the backing store;

the snapshot-creating module is further programmed to track the write while the write is still stored within the cache by:

maintaining a list of cached blocks of the backing store that includes blocks of the backing store that are cached; and

using the list of cached blocks of the backing store to ensure that the writes stored within the cache and associated with the blocks of the backing store that are cached are included in the snapshot of the backing store.

20. A non-transitory computer-readable medium comprising one or more computer-executable instructions that, when executed by at least one processor of a computing device, cause the computing device to:

identify a cache that implements write-back caching to selectively store at least one write to a backing store;

receive, while the write is stored within the cache, a request to create a snapshot of the backing store, where the write is to be included in the snapshot of the backing store;

create, in response to the request and while the write is still stored within the cache, the snapshot of the backing store by:

determining that the write is stored within the cache;

tracking the write while the write is still stored within the cache and while the snapshot is accessible to ensure that the write is included in the snapshot of the backing store;

provide read access to the snapshot without first flushing the write to the backing store by receiving, while the write is stored within the cache, a request to read from the snapshot;

satisfy the request to read from the snapshot.

Assignments (15)