File system replication

• US 20080010322A1
• Filed: 07/06/2006
• Published: 01/10/2008
• Est. Priority Date: 07/06/2006
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: Data Domain, Inc. (Dell Technologies Inc.)
• Inventors: Maheshwari, Umesh, Patterson, R. Hugo, Zhu, Ming Benjamin, Lee, Edward K.
• Granted Patent: US 7,882,064 B2
• Time in Patent Office: Days
• US Class Current: 707/201
• CPC Class Codes: G06F 16/178 Techniques for file synchronisation in file systems
• CPC Class Codes: G06F 16/184 implemented as replicated file system

Abstract

File system replication includes determining whether one of a plurality of files included in an original file system has been updated since a previous replication, the file having a plurality of data segments, and in the event that the file has been updated, locating among the plurality of data segments a previously stored data segment that is newly referenced by the file, and that does not require replication.

Claims

1. A method of file system replication comprising:

determining whether one of a plurality of files included in an original file system has been updated since a previous replication, the file having a plurality of data segments; and

in the event that the file has been updated, locating among the plurality of data segments a previously stored data segment that is newly referenced by the file, and that does not require replication.

2. A method as recited in claim 1, wherein in the event that the file has been updated, the method further comprises updating metadata associated with the file on the replicated file system.

3. A method as recited in claim 1, wherein in the event that the file has been updated, the method further comprises determining an updated portion of metadata associated with the file, and replicating the updated portion of metadata on the replicated file system.

4. A method as recited in claim 1, wherein in the event that the file has been updated, the method further comprises replicating a data segment reference associated with the file on the replicated file system.

5. A method as recited in claim 4, wherein the data segment reference is determined based at least in part on a content handle associated with the file.

6. A method as recited in claim 1, wherein in the event that the file has been updated, the method further comprises determining a data segment reference that has been updated, and replicating the updated data segment reference.

7. A method as recited in claim 1, wherein determining whether the file has been updated includes processing a log record.

8. A method as recited in claim 1, wherein determining whether the file has been updated includes processing a log record that includes a content handle associated with the file.

9. A method as recited in claim 1, wherein determining whether the file has been updated includes processing a log record that includes a previous content handle associated with the file at an earlier time, and a current content handle associated with a the file at the current time.

10. A method as recited in claim 1, wherein determining whether the file has been updated includes comparing a previous content handle associated with the file at an earlier time and a current content handle associated with the file at the current time.

11. A method as recited in claim 10, wherein at least one of the previous content handle and the current content handle is stored in a log record.

12. A method as recited in claim 10, wherein at least one of the previous content handle and the current content handle is stored in a file system snapshot.

13. A method as recited in claim 10, wherein at least one of the previous content handle and the current content handle is stored in the original file system.

14. A method as recited in claim 10, wherein at least one of the previous content handle and the current content handle is stored in the replicated file system.

15. A method as recited in claim 1, wherein determining whether the file has been updated includes performing a file system walk.

16. A method as recited in claim 1, wherein determining whether the file has been updated includes comparing a plurality of snapshots.

17. A method as recited in claim 1, wherein determining whether the file has been updated includes comparing a plurality of snapshots of the original file system.

18. A method as recited in claim 1, wherein determining whether the file has been updated includes comparing a plurality of snapshots of the file.

19. A method as recited in claim 1, wherein locating the previously stored data segment is based at least in part on a plurality of data segment references corresponding to the plurality of data segments.

20. A method as recited in claim 1, wherein locating the previously stored data segment includes looking up a data segment reference on the replicated file system.

21. A method as recited in claim 1, wherein locating the previously stored data segment includes looking up a data segment reference on the original file system.

22. A method as recited in claim 1, further comprising locating a previously not replicated data segment based on a content handle associated with the file, and replicating the previously not replicated data segment.

23. A method as recited in claim 22, wherein locating the previously not stored data segment based on the content handle includes dereferencing the content handle to obtain a plurality of data segment references, and determining whether each of the plurality of data segment references corresponds to a stored data segment that has been previously stored on the replicated file system.

24. A method as recited in claim 22, wherein the content handle is a recent content handle associated with a recent version of the file, and locating the previously not stored data segment is further based at least in part on a previous content handle associated with an earlier version of the file.

25. A method as recited in claim 24, wherein locating the previously not stored data segment further includes:

dereferencing the recent content handle to obtain a plurality of recent data segment references associated with the recent version of the file; and

dereferencing the previous content handles to obtain a plurality of previous data segment references associated with the earlier version of the file; and

determining a difference between the plurality of recent data segment references and the plurality of previous data segment references.

26. A method as recited in claim 24, wherein locating the previously not stored data segment includes determining whether the previous content handle has been stored on the replicated file system.

27. A method as recited in claim 26, further comprising, in the event that the previous content handle has not been stored on the replicated file system, dereferencing the recent content handle to obtain a plurality of recent data segment references associated with the recent version of the file.

28. A method as recited in claim 1, further comprising:

locating a previously not stored data segment;

preventing the previously not stored data segment from being deleted during garbage collection before the previously not stored data segment is replicated on the replicated file system; and

replicating the previously not stored data segment.

29. A method as recited in claim 28, further comprising maintaining a log record that maintains a reference to the previously not stored data segment.

30. A method as recited in claim 28, further comprising keeping a reference count of the previously stored data segment to be greater than zero at least until the previously not stored data segment is replicated.

31. A method as recited in claim 28, further comprising creating a place holder in the original file system to maintain a reference to the previously not stored data segment.

32. A method as recited in claim 1, further comprising initializing the replicated file system by copying the original file system.

33. A method as recited in claim 1, further comprising initializing the replicated file system by copying data segments that are included in the original file system.

34. A file system replicator comprising:

a processor configured to;

determine whether one of a plurality of files included in an original file system has been updated since a previous replication, the file having a plurality of data segments; and

in the event that the file has been updated, locate among the plurality of data segments a previously stored data segment that is newly referenced by the file, and that does not require replication; and

a memory coupled to the processor, configured to provide the processor with instructions.

35. A computer program product for file system replication, the computer program product being embodied in a computer readable medium and comprising computer instructions for:

determining whether one of a plurality of files included in an original file system has been updated since a previous replication, the file having a plurality of data segments; and

in the event that the file has been updated, locating among the plurality of data segments a previously stored data segment that is newly referenced by the file, and that does not require replication.