Recovery of file system data in file servers mirrored file system volumes

• US 7,096,379 B2
• Filed: 11/21/2003
• Issued: 08/22/2006
• Est. Priority Date: 10/04/2000
• Status: Expired due to Fees

• Current Assignee: Network Appliance Incorporated (NetApp, Inc.)
• Original Assignee: Network Appliance Incorporated (NetApp, Inc.)
• Inventors: Kleiman, Steven R., Viswanathan, Srinivasan
• Primary Examiner(s): Beausoliel, Robert W.
• Assistant Examiner(s): PUENTE, EMERSON C
• Application Number:
  US10/719,699
• Publication Number:
  US 20040153736A1
• Time in Patent Office: 1,005 Days
• Field of Search: 714 5- 8, 714/42, 707/202, 707/204, 711111-114, 711/161, 711/162
• US Class Current: 714/6.22
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: G06F 11/2064 while ensuring consistency
• CPC Class Codes: G06F 11/2082 Data synchronisation
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99955 Archiving or backup

Abstract

The invention provides a method and system for recovery of file system data in file servers having mirrored file system volumes. The invention makes use of a “snapshot” feature of a robust file system (the “WAFL File System”) disclosed in the Incorporated Disclosures, to rapidly determined which of two or more mirrored volumes is most up-to-date, and which file blocks of the most recent mirrored volume have been changed from each one of the mirrored file systems. In a preferred embodiment, among a plurality of mirrored volumes, the invention rapidly determines which is the most up-to-date by examining a consistency point number maintained by the WAFL File System at each mirrored volume. The invention rapidly pairwise determines what blocks are shared between that most up-to-date mirrored volume and each other mirrored volume, in response to a snapshot of the file system maintained at each mirrored volume and are stored in common pairwise between each mirrored volume and the most up-to-date mirrored volume. The invention re synchronizes only those blocks that have been changed between the common snapshot and the most up-to-date snapshot.

Claims

1. A method comprising:

creating at least one snapshot for each mirrored file system volume of a plurality of file system volumes;

including a consistency point value in said at least one snapshot indicating a sequence in which said at least one snapshot was generated;

examining the plurality of mirrored file system volumes for consistency point values; and

determining a most up-to-date said file system volume based on the consistency point values.

2. A method as in claim 1, further comprising:

determining a snapshot held in common between said most up-to-date said file system volume and at least one other mirrored file system volume of said plurality of mirrored file system volumes; and

selecting those file blocks changed between said snapshot held in common and said most up-to-date said file system volume.

3. A method as in claim 2, further comprising re-synchronizing said at least one other mirrored file system volume of said plurality of mirrored file system volumes with said most up-to-date said file system volume in response to said steps of selecting.

4. A method as in claim 3, wherein the step of re-synchronizing comprises copying the file blocks changed between said snapshot held in common and said most up-to-date said file system volume from said most up-to-date said file system volume to said at least one other mirrored file system volume.

5. A method as in claim 2, further comprising generating a new snapshot of said most up-to-date said file system volume.

6. A method as in claim 1, wherein the step of determining a most up-to-date said file system volume comprises determining the highest consistency point value.

19. A computer program product comprising program code that, when executed on a computer system, causes the computer system to effect the steps of any one of claims 1,2,3,6,5, and 4.

7. An apparatus comprising:

a plurality of mirrored file system volumes, each having at least one snapshot including an entire consistent file system, each said snapshot having a consistency point value indicating a sequence in which each said snapshot was generated;

a first comparison element capable of being coupled to a plurality of said consistency point values and capable of determining a most up-to-date mirrored file system volume of the plurality of mirrored file system volumes based on the consistency point values; and

a second comparison element, responsive to an output of said first comparison element, said second comparison element being capable of being coupled (a) to a first snapshot associated with said most up-to-date mirrored file system volume and (b) to a second snapshot associated with a second said volume, said second comparison element being capable of providing a selection of file blocks that differ between said second volume and said most up-to-date mirrored file system volume.

8. An apparatus as in claim 7, wherein said second snapshot is held in common between said most up-to-date mirrored file system volume and said second volume.

9. An apparatus as in claim 7 or 8, comprising an element capable of re-synchronizing said second volume in response to said second comparison element.

10. An apparatus as in claim 9, further comprising a network interface capable of receiving messages requesting that the data of the mirrored file system volumes be altered.

11. An apparatus as in claim 9, further comprising an element capable of including the consistency point value of each said snapshot in each said snapshot.

12. An apparatus as in claim 7, wherein the first comparison element determines said most up-to-date mirrored file system volume by determining a mirrored file system volume with an extreme consistency point value.

13. An apparatus as in claim 7, wherein the first comparison element determines the most up-to-date mirrored file system volume by determining a mirrored file system volume with the highest consistency point value.

14. An apparatus as in claim 13, further comprising an element capable of generating a new snapshot from said mirrored file system volume with the highest consistency point value.

15. An apparatus as in claim 7, further comprising a re-synchronization element capable of copying the selected file blocks from said most up-to-date mirrored file system volume to said second volume.

16. An apparatus as in claim 7, wherein said file system volumes include a RAID subsystem.

17. An apparatus as in claim 7, wherein said file system volumes include volumes for parallel stored systems.

18. An apparatus to maintain a plurality of mirrored file system volumes, the apparatus comprising:

a first element capable of creating at least one snapshot for each mirrored file system volume of the plurality of mirrored file system volumes and including a consistency point value in said at least one snapshot indicating a sequence in which said at least one snapshot was generated;

a second element capable of examining the snapshots of the plurality of mirrored file system volumes for consistency point values; and

a third element capable of determining a most up-to-date said file system volume based on the consistency point values.