Providing a snapshot of a subset of a file system

• US 20030158861A1
• Filed: 02/15/2002
• Published: 08/21/2003
• Est. Priority Date: 02/15/2002
• Status: Active Grant

• Current Assignee: SAP SE
• Original Assignee: International Business Machines Corporation
• Inventors: Sawdon, Wayne A., Schmuck, Frank B.
• Granted Patent: US 6,829,617 B2
• Time in Patent Office: Days
• US Class Current: 707/200
• CPC Class Codes: G06F 11/1435 using file system or storage system metadata
• CPC Class Codes: G06F 11/1458 Management of the backup or restore process
• CPC Class Codes: G06F 11/1469 Backup restoration techniques
• CPC Class Codes: G06F 11/2038 with a single idle spare processing component
• CPC Class Codes: G06F 11/2094 Redundant storage or storage space G06F11/2056 takes precedence
• CPC Class Codes: G06F 11/2097 maintaining the standby controller/processing unit updated initialisation or re-synchronisation thereof G06F11/1658 and subgroups
• CPC Class Codes: G06F 16/174 Redundancy elimination performed by the file system management of the data involved in backup or backup restore using de-duplication of the data G06F11/14
• CPC Class Codes: G06F 2201/84 Using snapshots, i.e. a logical point-in-time copy of the data
• CPC Class Codes: Y10S 707/99934 Query formulation, input preparation, or translation
• CPC Class Codes: Y10S 707/99943 Generating database or data structure, e.g. via user interface
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

A system, method and computer readable medium for providing a snapshot of a subset of a file system. A first snapshot of a first set of source files in a file system is generated. The first snapshot includes an inode corresponding to each source file in the first set of files. Stored in each inode is a first identifier associated with the first set of files and a second identifier associated with the time of the first snapshot. Next, a second snapshot of a second set of source files is taken. The second snapshot includes an inode corresponding to each source file in the second set of files. Stored in each inode are a first identifier and a second identifier. Subsequent snapshots are taken every first period and every second period for the first set of files and the second set of files, respectively.

Claims

1. A method for generating snapshots, comprising:

generating a first snapshot for a first plurality of source files in a file system, wherein the first snapshot includes an inode corresponding to each of the first plurality of source files;

storing, in each inode corresponding to each of the first plurality of source files, an identifier associated with the first plurality of source files; and

storing, in each inode corresponding to each of the first plurality of source files, an identifier associated with the time of the first snapshot.

This claim describes that snapshot sequences are taken periodically.

2. The method of claim 1, further comprising:

executing the generating step, the first storing step and the second storing step every first period.

3. The method of claim 2, further comprising:

generating a second snapshot for a second plurality of source files in a file system, wherein the second snapshot includes an inode corresponding to each of the second plurality of source files;

storing, in each inode corresponding to each of the second plurality of source files, an identifier associated with the second plurality of source files; and

storing, in each inode corresponding to each of the second plurality of source files, an identifier associated with the time of the second snapshot.

4. The method of claim 3, further comprising:

executing the second generating step, the third storing step and the fourth storing step every second period.

5. The method of claim 4, wherein at least some of the first plurality of source files and the second plurality of source files are not equivalent.

6. The method of claim 4, wherein the first period and the second period are not equivalent.

7. The method of claim 4, further comprising:

receiving a request to restore a desired snapshot;

determining, for each inode in the desired snapshot, whether a corresponding inode in the file system is available;

wherein if the corresponding inode in the file system is available, restoring the inode in the desired snapshot to the corresponding inode in the file system; and

wherein if the corresponding inode in the file system is not available, restoring the inode in the desired snapshot to an unallocated inode in the file system.

8. The method of claim 7, wherein an available inode comprises any one of:

an unallocated inode; and

an inode which corresponds to a source file which is a member of the same plurality of files that are included in the snapshot which has been restored.

9. The method of claim 7, wherein the second restoring step comprises, restoring the inode in the desired snapshot to an unallocated inode in the file system and updating a directory entry for the corresponding inode in the file system to reference the previously unallocated inode.

10. A method for restoring a snapshot, wherein a plurality of snapshots are available, comprising:

receiving a request to restore a desired snapshot;

determining, for each inode in the desired snapshot, whether a corresponding inode in a file system is available;

wherein if the corresponding inode in the file system is available, restoring the inode in the desired snapshot to the corresponding inode in the file system; and

wherein if the corresponding inode in the file system is not available, restoring the inode in the desired snapshot to an unallocated inode in the file system.

11. A computer readable medium including computer instructions for generating snapshots, the computer instructions comprising instructions for:

generating a first snapshot for a first plurality of source files in a file system, wherein the first snapshot includes an inode corresponding to each of the first plurality of source files;

storing, in each inode corresponding to each of the first plurality of source files, an identifier associated with the first plurality of source files; and

storing, in each inode corresponding to each of the first plurality of source files, an identifier associated with the time of the first snapshot.

12. The computer readable medium of claim 11, the computer instructions further comprising instructions for:

executing the instructions for generating, the first instructions for storing and the second instructions for storing every first period.

13. The computer readable medium of claim 12, the computer instructions further comprising instructions for:

generating a second snapshot for a second plurality of source files in a file system, wherein the second snapshot includes an inode corresponding to each of the second plurality of source files;

storing, in each inode corresponding to each of the second plurality of source files, an identifier associated with the second plurality of source files; and

storing, in each inode corresponding to each of the second plurality of source files, an identifier associated with the time of the second snapshot.

14. The computer readable medium of claim 13, the computer instructions further comprising instructions for:

executing the second instructions for generating, the third instructions for storing and the fourth instructions for storing every second period.

15. The computer readable medium of claim 14, wherein at least some of the first plurality of source files and the second plurality of source files are not equivalent.

16. The computer readable medium of claim 14, wherein the first period and the second period are not equivalent.

17. The computer readable medium of claim 14, the computer instructions further comprising instructions for:

receiving a request to restore a desired snapshot;

determining, for each mode in the desired snapshot, whether a corresponding inode in the file system is available;

wherein if the corresponding mode in the file system is available, restoring the inode in the desired snapshot to the corresponding mode in the file system; and

wherein if the corresponding mode in the file system is not available, restoring the mode in the desired snapshot to an unallocated mode in the file system.

18. The computer readable medium of claim 17, wherein an available inode comprises any one of:

an unallocated inode; and

an inode which corresponds to a source file which is a member of the same plurality of files that are included in the snapshot which has been restored.

19. The computer readable medium of claim 17, wherein the second instructions for restoring comprises, restoring the inode in the desired snapshot to an unallocated inode in the file system and updating a directory entry for the corresponding inode in the file system to reference the previously unallocated inode.

20. A computer readable medium including computer instructions for restoring a snapshot, wherein a plurality of snapshots are available, the computer instructions comprising instructions for:

receiving a request to restore a desired snapshot;

determining, for each inode in the desired snapshot, whether a corresponding inode in a file system is available;

wherein if the corresponding inode in the file system is available, restoring the inode in the desired snapshot to the corresponding inode in the file system; and

wherein if the corresponding inode in the file system is not available, restoring the inode in the desired snapshot to an unallocated inode in the file system.

21. A system for generating snapshots, comprising:

means for generating a first snapshot for a first plurality of source files in a file system, wherein the first snapshot includes an inode corresponding to each of the first plurality of source files;

means for storing, in each inode corresponding to each of the first plurality of source files, an identifier associated with the first plurality of source files; and

means for storing, in each inode corresponding to each of the first plurality of source files, an identifier associated with the time of the first snapshot.

22. The system of claim 21, further comprising:

means for executing the means for generating, the first means for storing and the second means for storing every first period.

23. The system of claim 22, further comprising:

means for generating a second snapshot for a second plurality of source files in a file system, wherein the second snapshot includes an inode corresponding to each of the second plurality of source files;

means for storing, in each inode corresponding to each of the second plurality of source files, an identifier associated with the second plurality of source files; and

means for storing, in each inode corresponding to each of the second plurality of source files, an identifier associated with the time of the second snapshot.

24. The system of claim 23, further comprising:

means for executing the second means for generating, the third means for storing and the fourth means for storing every second period.

25. The system of claim 24, wherein at least some of the first plurality of source files and the second plurality of source files are not equivalent.

26. The system of claim 24, wherein the first period and the second period are not equivalent.

27. The system of claim 24, further comprising:

means for receiving a request to restore a desired snapshot;

means for determining, for each inode in the desired snapshot, whether a corresponding inode in the file system is available;

means for restoring the inode in the desired snapshot to the corresponding inode in the file system; and

means for restoring the inode in the desired snapshot to an unallocated inode in the file system.

28. The system of claim 27, wherein an available inode comprises any one of:

an unallocated inode; and

an inode which corresponds to a source file which is a member of the same plurality of files that are included in the snapshot which has been restored.

29. The system of claim 27, wherein the second means for restoring comprises, means for restoring the inode in the desired snapshot to an unallocated inode in the file system and updating a directory entry for the corresponding inode in the file system to reference the previously unallocated inode.

30. A system for restoring a snapshot, wherein a plurality of snapshots are available, comprising:

means for receiving a request to restore a desired snapshot;

means for determining, for each inode in the desired snapshot, whether a corresponding inode in a file system is available;

means for restoring the inode in the desired snapshot to the corresponding inode in the file system; and

means for restoring the inode in the desired snapshot to an unallocated inode in the file system.

31. A system for generating snapshots, comprising:

a first snapshot for a first plurality of source files in a file system, wherein the first snapshot includes an inode corresponding to each of the first plurality of source files;

an identifier associated with the first plurality of source files, the identifier stored within each inode corresponding to each of the first plurality of source files; and

an identifier associated with the time of the first snapshot, the identifier stored within each inode corresponding to each of the first plurality of source files.

32. The system of claim 31, further comprising:

a second snapshot for a second plurality of source files in a file system, wherein the second snapshot includes an inode corresponding to each of the second plurality of source files;

an identifier associated with the second plurality of source files, the identifier stored within each inode corresponding to each of the second plurality of source files; and

an identifier associated with the time of the second snapshot, the identifier stored within each inode corresponding to each of the second plurality of source files.

33. The system of claim 32, wherein at least some of the first plurality of source files and the second plurality of source files are not equivalent.