Updating snapshots

• US 7,587,431 B1
• Filed: 09/28/2006
• Issued: 09/08/2009
• Est. Priority Date: 09/28/2006
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Joshi, Mayank, Rao, Mandavilli Navneeth
• Primary Examiner(s): Lee; Wilson
• Application Number:
  US11/540,998
• Time in Patent Office: 1,076 Days
• Field of Search: 707200-204, 707 1- 10, 707100-102
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1469 Backup restoration techniques
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: G06F 2201/84 Using snapshots, i.e. a logical point-in-time copy of the data
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

Previous version data is copied to a location in a collection of snapshot data, wherein the collection of snapshot data represents a state of a protected data set at a baseline time associated with a snapshot. Once the previous version data has been copied to the location in the collection of snapshot data, an index is updated to associate the location in the collection of snapshot data with the previous version data. A data region storage location from which the previous version data was copied to the location in the collection of snapshot data is making available for reuse once the index has been updated.

Claims

1. A computer-implemented method of updating a snapshot, comprising:

copying previous version data from a location in data region storage to a location in a collection of snapshot data, wherein;

the collection of snapshot data represents a state of a protected data set at a baseline time associated with a snapshot; and

the baseline time corresponds to a beginning of a protection window during which the protected data set is protected continuously and maintained over the protection window using continuous data protection, as opposed to protecting the protected data set only at specified points in time;

once the previous version data has been copied to the location in the collection of snapshot data, updating an index to associate the location in the collection of snapshot data with the previous version data; and

making available for reuse, once the index has been updated, the data region storage location from which the previous version data was copied.

2. The method as recited in claim 1, wherein the baseline time is a second baseline time and the method further comprises:

receiving, prior to copying, an indication to change from a first baseline time to the second baseline time, wherein in response to the indication the collection of snapshot data is modified; and

selecting, prior to copying, those previous version data stored in the data region storage which are associated with the second baseline time to be the previous version data which is copied.

3. The method as recited in claim 2, wherein determining, based at least in part on the new baseline time, that the previous version data is to be included in the collection of snapshot data comprises:

receiving a block map associated with the new baseline time; and

determining that the data region storage location is included in the block map.

4. The method as recited in claim 3, wherein the block map indicates for each of a plurality of storage locations comprising the protected data set, the respective corresponding location of an associated previous version data that was stored in that storage location of the protected data set at the new baseline time.

5. The method as recited in claim 1, wherein the previous version data includes data associated with one or more blocks comprising the protected data set.

6. The method as recited in claim 1, wherein copying includes overwriting obsolete snapshot data included in the collection of snapshot data.

7. The method as recited in claim 1, wherein making available for reuse comprises reclaiming and reallocating to a journal process associated with the protected data set.

8. The method as recited in claim 1, wherein a snapshot is able to be updated without locking a record.

9. The method as recited in claim 1, wherein a snapshot is able to be updated without requiring the use of an atomic operation formed by combining a plurality of unit steps.

16. The method as recited in claim 1, wherein the data region storage is used to store data that was present at a time during the protection window other than the baseline time.

19. The method as recited in claim 2 further comprising determining whether to change from the first baseline time to the second baseline time based at least in part on whether there is sufficient storage space to store newly received previous version data associated with an ending portion of the protection window.

10. A system for updating a snapshot, comprising:

a processor; and

a memory coupled with the processor, wherein the memory is configured to provide the processor with instructions which when executed cause the processor to;

copy previous version data from a location in data region storage to a location in a collection of snapshot data, wherein;

the collection of snapshot data represents a state of a protected data set at a baseline time associated with a snapshot; and

the baseline time corresponds to a beginning of a protection window during which the protected data set is protected continuously and maintained over the protection window using continuous data protection, as opposed to protecting the protected data set only at specified points in time;

once the previous version data has been copied to the location in the collection of snapshot data, update an index to associate the location in the collection of snapshot data with the previous version data; and

make available for reuse, once the index has been updated, the data region storage location from which the previous version data was copied.

12. The system as recited in claim 10, wherein the baseline time is a second baseline time and the memory is configured to provide the processor with further instructions which when executed cause the processor to:

receive, prior to copying, an indication to change from a first baseline time to the second baseline time, wherein in response to the indication the collection of snapshot data is modified; and

select, prior to copying, those previous version data stored in the data region storage which are associated with the second baseline time to be the previous version data which is copied.

13. The system as recited in claim 10, wherein the instructions for making available for reuse includes instructions for reclaiming and reallocating to a journal process associated with the protected data set.

17. The system as recited in claim 10, wherein the data region storage is used to store data that was present at a time during the protection window other than the baseline time.

20. The system as recited in claim 12 further comprising determining whether to change from the first baseline time to the second baseline time based at least in part on whether there is sufficient storage space to store newly received previous version data associated with an ending portion of the protection window.

11. A computer program product for updating a snapshot, the computer program product being embodied in a computer readable storage medium and comprising executable computer instructions for:

copying previous version data from a location in data region storage to a location in a collection of snapshot data, wherein;

the collection of snapshot data represents a state of a protected data set at a baseline time associated with a snapshot; and

the baseline time corresponds to a beginning of a protection window during which the protected data set is protected continuously and maintained over the protection window using continuous data protection, as opposed to protecting the protected data set only at specified points in time;

once the previous version data has been copied to the location in the collection of snapshot data, updating an index to associate the location in the collection of snapshot data with the previous version data; and

making available for reuse, once the index has been updated, the data region storage location from which the previous version data was copied to.

14. The computer program product as recited in claim 11, wherein the baseline time is a second baseline time and the computer program product further comprises computer instructions for:

receiving, prior to copying, an indication to change from a first baseline time to the second baseline time, wherein in response to the indication the collection of snapshot data is modified; and

selecting, prior to copying, those previous version data stored in the data region storage which are associated with the second baseline time to be the previous version data which is copied.

15. The computer program product as recited in claim 11, wherein the computer instructions for making available for reuse comprises computer instructions for reclaiming and reallocating to a journal process associated with the protected data set.

18. The computer program product as recited in claim 11, wherein the data region storage is used to store data that was present at a time during the protection window other than the baseline time.

21. The computer program product as recited in claim 14 further comprising determining whether to change from the first baseline time to the second baseline time based at least in part on whether there is sufficient storage space to store newly received previous version data associated with an ending portion of the protection window.