Recovering from storage transaction failures using checkpoints

• US 20060047925A1
• Filed: 08/24/2004
• Published: 03/02/2006
• Est. Priority Date: 08/24/2004
• Status: Active Grant

• Current Assignee: Veritas Technologies, LLC (Whitehouse Group Ltd.)
• Original Assignee: Symantec Operating Corporation (NortonLifeLock Inc.)
• Inventors: Perry, Robert
• Granted Patent: US 7,409,587 B2
• Time in Patent Office: Days
• US Class Current: 711/162
• CPC Class Codes: G06F 11/1461 Backup scheduling policy
• CPC Class Codes: G06F 11/1469 Backup restoration techniques
• CPC Class Codes: G06F 11/1474 in transactions G06F16/20 takes precedence

Abstract

The disclosed technology facilitates recovery from storage-related failures by checkpointing copy-on-write operation sequences. An operation sequence incorporating such checkpoints into a copy-on-write can include the following: receive a write request that identifies payload data to be written to a first data store, read original data associated with the first data store, copy the original data to a second data store, record transactional information associated with the write request, generate a first checkpoint to confirm the successful recordation of the transactional information and the successful copying of the original data to the second data store, write the payload data to the first data store, acknowledge a successful completion of the copy-on-write operation sequence, and generate a second checkpoint that confirms the successful completion of such operation sequence. The first and second checkpoints are used to form a pre-failure representation of one or more storage units (or parts thereof). The checkpoints can be stored with other transactional information, to facilitate recovery in the event of a failure, and can be used to facilitate the use of optimizations to process I/O operations.

Claims

1. A method of checkpointing a copy-on-write operation sequence, the method comprising:

(a) receiving a first write request identifying payload data to be written beginning at a first address of a first data store;

(b) reading original data associated with the first address of the first data store;

(c) copying the original data to a second data store beginning at a second address;

(d) recording transactional information associated with the first write request, the transactional information including indicia associated with the second address;

(e) generating a first checkpoint confirming the successful recordation of the transactional information and the successful copying of the original data to the second data store;

(f) writing the payload data to the first data store beginning at the first address;

(g) in response to successfully writing the payload data to the first data store, acknowledging a successful completion of the copy-on-write operation sequence; and

(h) generating a second checkpoint confirming the successful completion of the copy-on-write operation sequence.

2. The method of claim 1, wherein the transactional information further includes indicia associated with a time that the first write request was received.

3. The method of claim 1, wherein recordation of the transactional information comprises storing the first address, the second address, and a time that the first write request was received in at least one data structure.

4. The method of claim 1, further comprising:

based on at least one of the first and second checkpoints, forming a representation of at least one storage unit as it existed prior to a storage transaction failure.

5. The method of claim 4, wherein the storage transaction failure corresponds to at least one of a hardware failure and a power failure.

6. The method of claim 1, further comprising:

removing information associated with a second write request from at least one queue of a processor module based on finding the second checkpoint in the transactional information.

7. The method of claim 1, further comprising:

loading information associated with the first write request into at least one queue of a processor module based on finding the first checkpoint in the transactional information.

8. A method of recovering from a failure associated with a copy-on-write operation sequence, the method comprising:

identifying at least one write request queued prior to a failure, the write request corresponding to a plurality of operations in a copy-on-write operation sequence;

determining whether a first checkpoint was formed in response to completing a first portion of the copy-on-write operation sequence;

determining whether a second checkpoint was formed in response to completing at least a second portion of the copy-on-write operation sequence; and

based on at least one of the first and second checkpoints, processing the queued write request to at least partially recover from the failure, the write-request processing including;

upon failing to locate the first checkpoint, queuing the plurality of operations in the copy-on-write operation sequence for execution,

upon locating the first checkpoint and failing to locate the second checkpoint, queuing a subset of the plurality of operations for execution, the queued subset of operations including operations associated with the second portion, but not the first portion, of the copy-on-write operation sequence, and

upon locating the first and second checkpoints, removing the plurality of operations in the copy-on-write operation sequence from at least one operation queue.

9. The method of claim 8, wherein the failure corresponds to a hardware failure associated with a processor module.

10. The method of claim 8, wherein the first portion of the copy-on-write operation sequence includes at least one operation associated with copying original data stored at a location within a first data store to a second data store, the location within the first data store being identified by the queued write request.

11. The method of claim 8, wherein the second portion of the copy-on-write operation sequence includes at least one operation associated with writing payload data specified by the queued write request to a location within a first data store.

12. A method of recovering from a storage transaction failure, the method comprising:

receiving a write request identifying payload data to be written beginning at a first address of a first data store;

copying original data associated with the first address of the first data store to a second data store beginning at a second address;

recording transactional information associated with the write request, the transactional information including indicia associated with the first and second addresses and a time that the write request was received;

generating a first indicator confirming the recordation of the transactional information;

writing the payload data to the first data store beginning at the first address; and

in response to a storage transaction failure, using the first indicator and at least some of the transactional information to, at least partially, recover therefrom.

13. The method of claim 12, further comprising:

generating a second indicator confirming that the payload data was written to the first data store.

14. The method of claim 12, wherein the first indicator further confirms that the original data associated with the first address of the first data store is successfully copied to the second data store.

15. The method of claim 12, further comprising:

forming a representation of at least one storage unit as it existed prior to the storage transaction failure, based on at least some of the copied original data in the second data store.

16. The method of claim 12, wherein the storage transaction failure corresponds to at least one of a hardware failure and a power failure of a primary processor module.

17. The method of claim 16, further comprising:

generating a second indicator confirming that the payload data was written to the first data store; and

removing information associated with a second write request from at least one queue of a standby processor module based on finding the second indicator in the transactional information, wherein the standby processor module assumes the tasks of the primary processor module in response to the storage transaction failure.

18. The method of claim 17, further comprising:

loading information associated with a third write request into the at least one queue of the standby processor module based on finding the first indicator in the transactional information.

19. A method of recovering from a storage transaction failure, the method comprising:

detecting a storage transaction failure occurring at time T1;

identifying a first indicator associated with a first write request that was received prior to time T1, the first indicator confirming that data originally stored beginning at a first address specified by the first write request has been copied to a second address; and

forming a representation of at least one storage unit as it existed prior to the storage transaction failure based on at least some of the copied data.

20. The method of claim 19, wherein the storage transaction failure corresponds to at least one of a hardware failure and a power failure of a primary processor module.

21. The method of claim 20, further comprising:

identifying a second indicator confirming that payload data specified by the first write request was written to a data store beginning at the first address;

removing information associated with a second write request from at least one queue of a standby processor module based on the second indicator, wherein the standby processor module assumes the tasks of a primary processor module in response to the storage transaction failure.

22. The method of claim 21, further comprising:

loading information associated with the first write request into the at least one queue of the standby processor module based on the first indicator.