Standby file system with snapshot feature

• US 20030158862A1
• Filed: 02/15/2002
• Published: 08/21/2003
• Est. Priority Date: 02/15/2002
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Sawdon, Wayne A., Schmuck, Frank B., Haskin, Roger L., Eshel, Marc M.
• Granted Patent: US 6,959,310 B2
• Time in Patent Office: Days
• US Class Current: 707/200
• CPC Class Codes: G06F 16/10 File systems; File servers
• CPC Class Codes: Y10S 707/99931 Database or file accessing
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

A system, method and computer readable medium for providing a standby file system with snapshot feature is disclosed. A first snapshot of a primary file system is generated. Next, a standby file system restores the first snapshot of the primary file system in the standby file system and a snapshot of the standby file system is taken. Then, a second snapshot of the primary file system is taken and a data set capturing the differences between the first snapshot of the primary file system and a previous data set of the primary file system is generated. Subsequently, the data set is applied to the standby file system. Upon unavailability of the primary file system, the standby file system is initialized as the new primary file system. Upon recovery of the old primary file system, the old primary file system is initialized as a new standby file system.

Claims

1. A method for providing a standby file system, comprising the steps of:

generating a first snapshot of a first file system, wherein the first file system is a primary file system;

restoring in a second file system the first snapshot, wherein the second file system is a standby file system;

generating a first snapshot of the second file system;

generating a second snapshot of the first file system;

generating a data set of the first file system, wherein the data set includes the changes that have occurred in the first file system between the most recent snapshot of the first file system and a previous data set of the first file system which was applied to the second file system;

applying the data set in the second file system;

generating a second snapshot of the second file system;

periodically executing the third generating step, fourth generating step, the applying step and the fifth generating step.

2. The method of claim 1, further comprising the steps of:

applying, upon unavailability of the first file system, a most recent data set of the first file system in the second file system;

initializing the second file system as the primary file system;

restoring, upon recovery of the first file system, a most recent snapshot of the first file system in the first file system; and

initializing the first file system as the standby file system.

3. The method of claim 2, further comprising the steps of:

generating a snapshot of the second file system;

generating a data set of the second file system, wherein the data set includes the changes that have occurred in the second file system between the most recent snapshot of the second file system and a previous data set of the second file system which was applied to the first file system;

applying the data set in the first file system;

generating a snapshot of the first file system; and

periodically executing the sixth generating step, the seventh generating step, the third applying step and the eighth generating step.

4. The method of claim 3, further comprising the steps of:

initializing the second file system as the standby file system; and

initializing the first file system as the primary file system.

5. The method of claim 1, further comprising the steps of:

applying, upon unavailability of the first file system, a most recent data set of the first file system in the second file system;

initializing the second file system as the primary file system;

generating one or more snapshots of the second file system;

restoring, upon recovery of the first file system, a most recent snapshot of the first file system in the first file system; and

initializing the first file system as the standby file system.

6. The method of claim 5, further comprising the steps of:

generating a snapshot of the second file system;

generating a data set of the second file system, wherein the data set includes the changes that have occurred in the second file system between the most recent snapshot of the second file system and a previous data set of the second file system which was applied to the first file system;

applying the data set in the first file system;

generating a snapshot of the first file system; and

periodically executing the seventh generating step, the eighth generating step, the third applying step and the ninth generating step.

7. The method of claim 6, further comprising the steps of:

initializing the second file system as the standby file system; and

initializing the first file system as the primary file system.

21. The method of claim 5, further comprising the step of:

storing an identifier in the superblock of the first file system upon each application of a data set to the first file system, wherein the identifier identifies the data set that was applied.

22. The method of claim 21, further comprising the step of:

storing an identifier in the superblock of the second file system upon each application of a data set to the second file system, wherein the identifier identifies the data set that was applied.

23. The method of claim 1, wherein the fourth generating step comprises:

generating a data set of the first file system, wherein the data set includes the changes that have occurred in the first file system between the most recent snapshot of the first file system and the next most recent snapshot of the first file system.

24. The method of claim 1, wherein the fourth generating step comprises:

generating a data set of the first file system, wherein the data set includes the changes that have occurred in the first file system between the most recent snapshot of the first file system and the last data set of the first file system that was applied to the second file system.

25. The method of claim 6, wherein the eighth generating step comprises:

generating a data set of the second file system, wherein the data set includes the changes that have occurred in the second file system between the most recent snapshot of the second file system and the next most recent snapshot of the second file system.

26. The method of claim 6, wherein the eighth generating step comprises:

generating a data set of the second file system, wherein the data set includes the changes that have occurred in the second file system between the most recent snapshot of the second file system and the last data set of the second file system that was applied to the first file system.

27. The method of claim 4, further comprising the step of:

generating a snapshot of the first file system, wherein the snapshot is not taken for the purpose of providing a standby file system.

28. The method of claim 27, further comprising the step of:

generating a snapshot of the second file system, wherein the snapshot is not taken for the purpose of providing a standby file system.

32. The method of claim 4, further comprising the steps of:

generating a snapshot of the first file system, wherein the snapshot is not taken for the purpose of providing a standby file system; and

providing the snapshot to a processor for creation of a tape backup comprising the snapshot.

33. The method of claim 4, wherein the second file system is a standby file system for a third file system.

34. The method of claim 4, wherein the first file system is a standby file system for a third file system.

8. A computer readable medium including computer instructions for providing a standby file system, the computer instructions comprising instructions for:

generating a first snapshot of the second file system;

generating a second snapshot of the first file system;

generating a data set of the first file system, wherein the data set includes the changes that have occurred in the first file system between the most recent snapshot of the first file system and a previous data set of the first file system which was applied to the second file system;

applying the data set in the second file system;

generating a second snapshot of the second file system;

periodically executing the third generating instructions, fourth generating instructions, the applying instructions and the fifth generating instructions.

9. The computer readable medium of claim 8, the computer instructions further comprising instructions for:

applying, upon unavailability of the first file system, a most recent data set of the first file system in the second file system;

initializing the second file system as the primary file system;

restoring, upon recovery of the first file system, a most recent snapshot of the first file system in the first file system; and

initializing the first file system as the standby file system.

10. The computer readable medium of claim 9, the computer instructions further comprising instructions for:

generating a snapshot of the second file system;

generating a data set of the second file system, wherein the data set includes the changes that have occurred in the second file system between the most recent snapshot of the second file system and previous data set of the second file system which was applied to the first file system;

applying the data set in the first file system;

generating a snapshot of the first file system; and

periodically executing the sixth generating instructions, the seventh generating instructions, the third applying instructions and the eighth generating instructions.

11. The computer readable medium of claim 10, the computer instructions further comprising instructions for:

initializing the second file system as the standby file system; and

initializing the first file system as the primary file system.

12. The computer readable medium of claim 8, the computer instructions further comprising instructions for:

applying, upon unavailability of the first file system, a most recent data set of the first file system in the second file system;

initializing the second file system as the primary file system;

generating one or more snapshots of the second file system;

restoring, upon recovery of the first file system, a most recent snapshot of the first file system in the first file system; and

initializing the first file system as the standby file system.

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

generating a snapshot of the second file system;

generating a data set of the second file system, wherein the data set includes the changes that have occurred in the second file system between the most recent snapshot of the second file system and previous data set of the second file system which was applied to the first file system;

applying the data set in the first file system;

generating a snapshot of the first file system; and

periodically executing the seventh generating instructions, the eighth generating instructions, the third applying instructions and the ninth generating instructions.

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

initializing the second file system as the standby file system; and

initializing the first file system as the primary file system.

15. A system for providing a standby file system, comprising:

means for generating a first snapshot of a first file system, wherein the first file system is a primary file system;

means for restoring in a second file system the first snapshot, wherein the second file system is a standby file system;

means for generating a first snapshot of the second file system;

means for generating a second snapshot of the first file system;

means for generating a data set of the first file system, wherein the data set includes the changes that have occurred in the first file system between the most recent snapshot of the first file system and previous data set of the first file system which was applied to the second file system;

means for applying the data set in the second file system;

means for generating a second snapshot of the second file system;

means for periodically executing the third means for generating, fourth means for generating, the means for applying and the fifth means for generating.

16. The system of claim 15, further comprising:

means for applying, upon unavailability of the first file system, a most recent data set of the first file system in the second file system;

means for initializing the second file system as the primary file system;

means for restoring, upon recovery of the first file system, a most recent snapshot of the first file system in the first file system; and

means for initializing the first file system as the standby file system.

17. The system of claim 16, further comprising:

means for generating a snapshot of the second file system;

means for generating a data set of the second file system, wherein the data set includes the changes that have occurred in the second file system between the most recent snapshot of the second file system and previous data set of the second file system which was applied to the first file system;

means for applying the data set in the first file system;

means for generating a snapshot of the first file system; and

means for periodically executing the sixth means for generating, the seventh means for generating, the third means for applying and the eighth means for generating.

18. The system of claim 17, further comprising:

means for initializing the second file system as the standby file system; and

means for initializing the first file system as the primary file system.

19. The system of claim 15, further comprising:

means for applying, upon unavailability of the first file system, a most recent data set of the first file system in the second file system;

means for initializing the second file system as the primary file system;

means for generating one or more snapshots of the second file system;

means for restoring, upon recovery of the first file system, a most recent snapshot of the first file system in the first file system; and

means for initializing the first file system as the standby file system.

20. The system of claim 19, further comprising:

means for generating a snapshot of the second file system;

means for generating a data set of the second file system, wherein the data set includes the changes that have occurred in the second file system between the most recent snapshot of the second file system and a previous data set of the second file system which was applied to the first file system;

means for applying the data set in the first file system;

means for generating a snapshot of the first file system; and

means for periodically executing the seventh means for generating, the eighth means for generating, the third means for applying and the ninth means for generating.

29. A system for providing a standby file system, comprising:

a first snapshot of a first file system, wherein the first file system is a primary file system;

means for restoring in a second file system the first snapshot, wherein the second file system is a standby file system;

a first snapshot of the second file system;

a second snapshot of the first file system;

a data set of the first file system, wherein the data set includes the changes that have occurred in the first file system between the most recent snapshot of the first file system and a previous data set of the first file system which was applied to the second file system;

means for applying the data set in the second file system; and

a second snapshot of the second file system.

30. The system of claim 29, further comprising:

a most recent data set of the first file system, wherein the most recent data set is applied to the second file system, upon unavailability of the first file system;

means for initializing the second file system as the primary file system;

a most recent snapshot of the first file system, wherein the most recent snapshot is restored in the first file system, upon recovery of the first file system; and

means for initializing the first file system as the standby file system.

31. The system of claim 30, further comprising:

a snapshot of the second file system;

a data set of the second file system, wherein the data set includes the changes that have occurred in the second file system between the most recent snapshot of the second file system and a previous data set of the second file system which was applied to the first file system;

means for applying the data set in the first file system;

a snapshot of the first file system.