Rapid Recovery From Downtime Of Mirrored Storage Device

• US 20140281272A1
• Filed: 03/13/2013
• Published: 09/18/2014
• Est. Priority Date: 03/13/2013
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Loaiza, Juan R., Umamageswaran, Kothanda, Shi, Jia, Tsukerman, Alex, Friedman, David, Tao, Zuoyu
• Granted Patent: US 10,380,021 B2
• Time in Patent Office: Days
• US Class Current: 711/144
• CPC Class Codes: G06F 11/2058 using more than 2 mirrored copies
• CPC Class Codes: G06F 11/2082 Data synchronisation
• CPC Class Codes: G06F 12/0804 with main memory updating G06F12/0806 takes precedence
• CPC Class Codes: G06F 12/0868 Data transfer between cache memory and other subsystems, e.g. storage devices or host systems
• CPC Class Codes: G06F 12/12 Replacement control
• CPC Class Codes: G06F 2212/222 Non-volatile memory
• CPC Class Codes: G06F 2212/262 configured as RAID
• CPC Class Codes: G06F 2212/286 Mirrored cache memory

Abstract

No-loss rapid recovery performs resynchronization efficiently while concurrently allowing availability to mirrored data on the storage device. No-loss rapid recovery has two stages and involves storage devices that have both a non-volatile cache and primary storage and that operate as mirror buddies. The first stage is referred to herein as the buddy-retention stage. During the buddy-retention stage, writes to mirrored data are not performed on the offline mirror buddy but are performed on the online mirror buddy. The mirrored data changed in the online mirrored buddy is retained in the non-volatile cache of the retention buddy. The next stage is referred to herein as the rapid resynchronization stage. In this stage, the changed mirrored data retained by the retention buddy for no-loss rapid recovery is used to resynchronize the offline buddy. The storage device is resynchronized using the changed mirrored data retained in the cache of the mirror buddy.

Claims

1. A method, comprising steps of:

in response to receiving one or more requests to write a plurality of data blocks;

a first storage device writing said plurality of data blocks to a non-volatile cache of a primary store of said first storage device, said primary store of said first storage device storing said plurality of data blocks, wherein said first storage device is one of a mirrored set of storage devices for mirroring data that includes said plurality of data blocks;

tracking said plurality of data blocks as dirty data blocks that have not been written to a second storage device;

retaining said plurality of data blocks in said non-volatile cache of said first storage device; and

resynchronizing said second storage device using said plurality of data blocks retained in said non-volatile cache of said first storage device.

2. The method of claim 1, wherein the step of resynchronizing includes:

a storage device client of said mirrored set of storage devices transmitting a request for said plurality of data blocks to said first storage device;

said first storage device retrieving said plurality of data blocks from said non-volatile cache and returning said plurality of data blocks to said storage device client; and

said storage device client transmitting a request to said second storage device to write said plurality of data blocks.

3. The method of claim 1, wherein the steps further include:

a storage device client of said mirrored set of storage devices transmitting said one or more requests to write said plurality of data blocks; and

said storage device client of said mirrored set of storage devices tracking in a list of dirty data blocks said plurality of data blocks.

4. The method of claim 3, wherein the step of resynchronizing includes:

based on the list of dirty data blocks, said storage device client identifying data blocks to resynchronize in said second storage device, wherein identifying data blocks to resynchronize includes identifying said plurality of data blocks;

said storage device client of said mirrored set of storage devices transmitting a request for said plurality of data blocks to said first storage device;

said first storage device retrieving said plurality of data blocks from said non-volatile cache and returning said plurality of data blocks to said storage device client; and

said storage device client transmitting a request to said second storage device to write said plurality of data blocks.

5. The method of claim 1, wherein the step of retaining is performed in response to said one or more requests specifying to retain the plurality of data blocks.

6. The method of claim 1, the steps further including:

in response to receiving one or more requests to write another plurality of data blocks;

a third storage device writing said another plurality of data blocks to a non-volatile cache of a primary store of said third storage device, said primary store of said third storage device storing said another plurality of data blocks, wherein said third storage device is one of said mirrored set of storage devices;

tracking said another plurality of data blocks as dirty data blocks that have not been written to said second storage device;

retaining said plurality of data blocks in said non-volatile cache of a primary store of said third storage device; and

resynchronizing said second storage device using said plurality of data blocks retained in said non-volatile cache of said third storage device.

7. The method of claim 1, the steps further including:

receiving a message indicating to cease retaining said plurality of data blocks; and

in response to receiving said message, ceasing to retain said plurality of data blocks.

8. The method of claim 1, wherein ceasing to retain includes discarding said plurality of data blocks from said non-volatile cache of said primary store of said first storage device.

9. The method of claim 1, wherein said step of retaining is performed while performing cache replacement on said non-volatile cache.

10. The method of claim 9, wherein said writing said plurality of data blocks to a non-volatile cache of a primary store of said first storage device is performed as part of a write-through operation, said write through operation including writing said plurality of data blocks to said primary store.

11. A method, comprising steps of:

in response to receiving one or more requests to write a plurality of data blocks;

a first storage device writing said plurality of data blocks to a non-volatile cache of a primary store of said first storage device, said primary store of said first storage device storing said plurality of data blocks, wherein said first storage device is one of a mirrored set of storage devices for mirroring data that includes said plurality of data blocks;

while performing cache replacement, retaining said plurality of data blocks in said non-volatile cache of said first storage device;

said first storage device receiving a message indicating to cease retaining said plurality of data blocks; and

in response to receiving said message, said first storage device ceasing to retain said plurality of data blocks.

12. The method of claim 11, wherein said writing said plurality of data blocks to a non-volatile cache of a primary store of said first storage device is performed as part of a write-through operation, said write-through operation including writing said plurality of data blocks to said primary store.

13. The method of claim 11, wherein said writing said plurality of data blocks to a non-volatile cache of a primary store of said first storage device is performed as part of a write-back operation.

14. One or more non-transitory storage media storing instructions which, when executed by one or more computing devices, cause performance of steps:

in response to receiving one or more requests to write a plurality of data blocks;

a first storage device writing said plurality of data blocks to a non-volatile cache of a primary store of said first storage device, said primary store of said first storage device storing said plurality of data blocks, wherein said first storage device is one of a mirrored set of storage devices for mirroring data that includes said plurality of data blocks;

tracking said plurality of data blocks as dirty data blocks that have not been written to a second storage device;

retaining said plurality of data blocks in said non-volatile cache of said first storage device; and

resynchronizing said second storage device using said plurality of data blocks retained in said non-volatile cache of said first storage device.

15. The one or more non-transitory storage media of claim 14, wherein the step of resynchronizing includes:

a storage device client of said mirrored set of storage devices transmitting a request for said plurality of data blocks to said first storage device;

said first storage device retrieving said plurality of data blocks from said non-volatile cache and returning said plurality of data blocks to said storage device client; and

said storage device client transmitting a request to said second storage device to write said plurality of data blocks.

16. The one or more non-transitory storage media of claim 14, wherein the steps further include:

a storage device client of said mirrored set of storage devices transmitting said one or more requests to write said plurality of data blocks; and

said storage device client of said mirrored set of storage devices tracking in a list of dirty data blocks said plurality of data blocks.

17. The one or more non-transitory storage media of claim 16, wherein the step of resynchronizing includes:

based on the list of dirty data blocks, said storage device client identifying data blocks to resynchronize in said second storage device, wherein identifying data blocks to resynchronize includes identifying said plurality of data blocks;

said storage device client of said mirrored set of storage devices transmitting a request for said plurality of data blocks to said first storage device;

said first storage device retrieving said plurality of data blocks from said non-volatile cache and returning said plurality of data blocks to said storage device client; and

said storage device client transmitting a request to said second storage device to write said plurality of data blocks.

18. The one or more non-transitory storage media of claim 14, wherein the step of retaining is performed in response to said one or more requests specifying to retain the plurality of data blocks.

19. The one or more non-transitory storage media of claim 14, the steps further including:

in response to receiving one or more requests to write another plurality of data blocks;

a third storage device writing said another plurality of data blocks to a non-volatile cache of a primary store of said third storage device, said primary store of said third storage device storing said another plurality of data blocks, wherein said third storage device is one of said mirrored set of storage devices;

tracking said another plurality of data blocks as dirty data blocks that have not been written to said second storage device;

retaining said plurality of data blocks in said non-volatile cache of a primary store of said third storage device; and

resynchronizing said second storage device using said plurality of data blocks retained in said non-volatile cache of said third storage device.

20. The one or more non-transitory storage media of claim 14, the steps further including:

receiving a message indicating to cease retaining said plurality of data blocks; and

in response to receiving said message, ceasing to retain said plurality of data blocks.

21. The one or more non-transitory storage media of claim 14, wherein ceasing to retain includes discarding said plurality of data blocks from said non-volatile cache of said primary store of said first storage device.

22. The one or more non-transitory storage media of claim 14, wherein said step of retaining is performed while performing cache replacement on said non-volatile cache.

23. The one or more non-transitory storage media of claim 22, wherein said writing said plurality of data blocks to a non-volatile cache of a primary store of said first storage device is performed as part of a write-through operation, said write through operation including writing said plurality of data blocks to said primary store.

24. One or more non-transitory storage media storing instructions which, when executed by one or more computing devices, cause performance of steps:

in response to receiving one or more requests to write a plurality of data blocks;

a first storage device writing said plurality of data blocks to a non-volatile cache of a primary store of said first storage device, said primary store of said first storage device storing said plurality of data blocks, wherein said first storage device is one of a mirrored set of storage devices for mirroring data that includes said plurality of data blocks;

while performing cache replacement, retaining said plurality of data blocks in said non-volatile cache of said first storage device;

said first storage device receiving a message indicating to cease retaining said plurality of data blocks; and

in response to receiving said message, said first storage device ceasing to retain said plurality of data blocks.

25. The one or more non-transitory storage media of claim 24, wherein said writing said plurality of data blocks to a non-volatile cache of a primary store of said first storage device is performed as part of a write-through operation, said write-through operation including writing said plurality of data blocks to said primary store.

26. The one or more non-transitory storage media of claim 24, wherein said writing said plurality of data blocks to a non-volatile cache of a primary store of said first storage device is performed as part of a write-back operation.