System and method for storage of snapshot metadata in a remote file

• US 20030182322A1
• Filed: 03/19/2002
• Published: 09/25/2003
• Est. Priority Date: 03/19/2002
• Status: Active Grant

• Current Assignee: NetApp, Inc.
• Original Assignee: Network Appliance Incorporated (NetApp, Inc.)
• Inventors: Manley, Stephen L., Edwards, John K., Chen, Raymond C.
• Granted Patent: US 7,043,485 B2
• Time in Patent Office: Days
• US Class Current: 707/201
• CPC Class Codes: G06F 16/184 implemented as replicated file system
• CPC Class Codes: Y10S 707/99954 Version management

Abstract

In a system and method for updating a remote replicated destination file system snapshot with changes in a source file system snapshot, the snapshot being associated with a qtree (or other sub-organization of the file system volume), a qtree metadata file on the destination in provided. The qtree metadata file resides, in the destination volume, and outside the qtree structure. The metadata file stores state information with respect to each qtree. This metadata file resides at a known location in the destination volume. The metadata file can include a plurality of fixed length records having respective fields for storing various information including qtree-specific information, and can be part of a hidden metadata directory.

Claims

1. A metadata file for storing information related to a sub-organization of a volume:

a plurality of fixed length records each including a plurality of fields having state information related to the sub-organization, the records being stored in the metadata file at a location outside of the sub-organization.

2. The metadata file as set forth in claim 1 wherein the sub-organization comprises a qtree and at least one of the fields is related to a qtree identifier.

3. The metadata file as set forth in claim 2 wherein the fields include a “

short”

name field pointing to a full qtree name on a directory.

4. The metadata file as set forth in claim 2, wherein the fields include a qtree root inode and generation number field.

5. The metadata file as set forth in claim 2 wherein the fields include a field having information related to a latest exported snapshot created from an active file system destination replica snapshot of a source snapshot.

6. The metadata file as set forth in claim 2 wherein the fields include spare space for expansion of information.

7. The metadata file as set forth in claim 2 wherein the metadata file is associated with a directory that is hidden from users and predetermined system applications and processes.

8. The metadata file as set forth in claim 2 wherein predetermined of the fields include performance-sensitive information that is maintained in a buffer cache of a file server during operation of the file server.

9. The metadata file as set forth in claim 8 wherein predetermined of the fields include performance-insensitive information that is maintained on disk and only written into the buffer cache of the file server when required to perform an operation therewith.

10. The metadata file as set forth in claim 2 further comprising a major version number and a minor version number stored at a predetermined location.

11. The metadata file as set forth in claim 10 wherein the major version number is representative of a predetermined format of the record or size of the record, whereby a change of the version number represents a change of the format or size.

12. The metadata file as set forth in claim 11 wherein the minor version number is representative of a number of fields in the record.

13. The metadata file as set forth in claim 12 wherein the file is adapted, when a major version of the file matches a major version recognized by a file system, to be reverted, with any fields not recognized by the file system set to a non-informational state, to a latest minor version recognized by the file system.

14. A method for comparing and conforming a version metadata file that stores records containing state information about a sub-organization of a volume to a known version in a file system kernel comprising the steps of:

comparing a major version and a minor version of the metadata file to a known major version and a known minor version recognized by the kernel;

updating an older major version or an older minor version of the metadata file to the reflect a latest known major version and a latest known minor version, respectively

where the major version of the file matches the latest known major version, and the minor version of the metadata file is newer than the latest known minor version, converting any fields not recognized by the kernel to a non-informational state and resetting the minor version of the file to the latest known minor version; and

where the major version of the metadata file is newer than the latest known major version, entering a corrective state.

15. The method as set forth in claim 14 wherein the step of entering the corrective state comprises a halt by the kernel in processing the metadata file.

16. The method as set forth in claim 14 wherein the sub-organization comprises a qtree and the metadata file is located outside the qtree.

17. The method as set forth in claim 14 wherein information defining the major version and the minor version in stored in a header associated with a plurality of records in the metadata file.

18. The method as set forth in claim 17 wherein each of the plurality of records include an entry defining a qtree with which the metadata file is associated, a latest exported snapshot ID associated with the qtree and a sort name that points to a full qtree name.

19. The method as set forth in claim 14 wherein the step of converting the fields not recognized includes associating the fields not recognized with a spare space having a zeroed value.

20. A method for recording changes to a metadata file that stores records containing state information about a sub-organization of a volume to a known version in a file system kernel comprising the steps of:

storing the changes in a non-volatile memory of a file server adapted to retain the changes upon unintended shutdown; and

if an unintended shutdown occurs, replaying changes logged in the non-volatile memory and updating the metadata file with the changes.

21. A method for storing information related to a sub-organization of a volume in a metadata file comprising:

defining a plurality of fixed length records each including a plurality of fields having state information related to the sub-organization, the records being stored in the metadata file at a location outside of the sub-organization.

22. The method as set forth in claim 21 wherein the sub-organization comprises a qtree and at least one of the fields is related to a qtree identifier.

23. The method as set forth in claim 22 further comprising defining the fields to include a “

short”

name field pointing to a full qtree name on a directory.

24. The method as set forth in claim 22 further comprising defining the fields to include a qtree root inode and generation number field.

25. The method as set forth in claim 22 further comprising defining the fields to include a field having information related to a latest exported snapshot created from an active file system destination replica snapshot of a source snapshot.

26. The method as set forth in claim 22 further comprising defining the fields to include spare space for expansion of information.

27. The method as set forth in claim 23 further comprising associating the metadata file with a directory that is hidden from users and predetermined system applications and processes.

28. The method as set forth in claim 23 further comprising denoting predetermined of the fields to include performance-sensitive information that is maintained in a buffer cache of a file server during operation of the file server.