System and method for restoring data on demand for instant volume restoration

• US 20070124341A1
• Filed: 04/24/2006
• Published: 05/31/2007
• Est. Priority Date: 02/10/2003
• Status: Active Grant

• Current Assignee: NetApp, Inc.
• Original Assignee: NetApp, Inc.
• Inventors: Manley, Stephen, Edwards, John, Zheng, Ling, Lango, Jason, Ackaouy, Emmanuel, Eastham, Paul, English, Robert, Cho, Yong
• Granted Patent: US 7,809,693 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/10 File systems; File servers

Abstract

A technique is disclosed for restoring data of sparse volumes, where one or more block pointers within the file system structure are marked as ABSENT, and fetching the appropriate data from an alternate location on demand. Client data access requests to the local storage system initiate a restoration of the data from a backing store as required. A demand generator can also be used to restore the data as a background process by walking through the sparse volume and restoring the data of absent blocks. A pump module is also disclosed to regulate the access of the demand generator. Once all the data has been restored, the volume contains all data locally, and is no longer a sparse volume.

Claims

1. A method for use with a storage device, the method comprising the steps of:

detecting a failed volume;

replacing the failed volume with a new volume;

creating an organization of infrastructure for the new volume;

populating the new volume with pointers to one or more blocks indicating that data for the blocks is located other than locally; and

restoring data of the one or more blocks on demand.

2. The method of claim 1, further comprising the step of indicating, by absent pointers, that data for the blocks is located other than locally, wherein the blocks are absent blocks.

3. The method of claim 1, further comprising the step of restoring the data with client access requests.

4. The method of claim 1, further comprising the step of restoring the data with a demand generator.

5. The method of claim 1, further comprising the step of restoring the data from a remote backup volume.

6. The method of claim 1 further comprising the step of processing data access operations directed to the new volume.

7. The method of claim 6 wherein the data access operations comprise write operations.

25. The method of claim 1 further comprising the step of initiating a back up operation of the new volume to a remote backup volume.

8. A method for use with a storage device, the method comprising the steps of

A. determining if a volume contains blocks having data located other than locally;

B. if so, scanning the volume for the blocks having data located other than locally; and

C. in response to a block having data located other than locally

i) sending a request for data to a remote volume;

ii) receiving the requested data; and

iii) storing the data locally.

9. The method of claim 8, further comprising the step of continuing steps A, B, and C until all blocks on the volume are located locally.

10. The method of claim 8, further comprising the step of incrementally scanning the blocks of the volume.

11. The method of claim 8, further comprising the step of scanning the blocks for a special value denoting that the data is stored other than locally.

12. The method of claim 11, further comprising the step of scanning the blocks for an absent value for the special value.

13. The method of claim 8, further comprising the step of determining if a volume contains blocks having data stored other than locally by detecting an indicator.

14. The method of claim 8, further comprising the step of storing the data locally by performing a write allocation of the data.

15. The method of claim 8, further comprising the step of sending the request for data to a backing store as the remote volume.

16. The method of claim 8 wherein the requested data is received over a special load path.

17. The method of claim 16, wherein the requested data is marked to indicate that it is not necessary to store in a cache.

18. The method of claim 8, wherein the blocks are scanned in phases, including an inode file, directories, and files.

19. The method of claim 8, wherein the blocks are scanned in phases, including an inode file, special data containers, directories, and files.

20. The method of claim 8, wherein the blocks are scanned in logical succession.

21. The method of claim 20, wherein the blocks are scanned incrementally by file ID number.

22. The method of claim 8, further comprising the step of performing a read-ahead operation for sequential requests for data.

23. The method of claim 8 wherein a demand generator performs steps A, B, and C.

24. The method of claim 23, wherein multiple demand generators are used in parallel.

26. A method for use with a storage device the method, comprising the steps of:

monitoring a demand generator access from a sparse volume to a backing store; and

in the event the access is greater than or equal to a maximum threshold, regulating the access of the demand generator.

27. The method of claim 26, further comprising the steps of:

monitoring client access from the sparse volume to the backing store;

comparing the demand generator access to available resources and resources required by the client access; and

in the event the available resources are less than the resources required by the client access, regulating the access of the demand generator.

28. The method of claim 26, further comprising the step of regulating the access of the demand generator by reducing a rate of the access.

29. The method of claim 26, further comprising the step of regulating the access of the demand generator by pausing the access.

30. The method of claim 26, wherein a pump module performs the steps of monitoring and regulating.

31. A system for use with a storage device, the system comprising:

means for detecting a failed volume;

means for replacing the failed volume with a new volume;

means for creating an organization of infrastructure for the new volume;

means for populating the new volume with pointers to one or more blocks indicating that data for the blocks is located other than locally; and

means for restoring data of the one or more blocks on demand.

32. The system of claim 31 further comprising means for initiating a backup operation of the new volume to a remote backup volume.