SNAPSHOT- PROTECTED CONSISTENCY CHECKING FILE SYSTEMS

• US 20150186217A1
• Filed: 12/31/2013
• Published: 07/02/2015
• Est. Priority Date: 12/31/2013
• Status: Active Grant

• Current Assignee: NetApp, Inc.
• Original Assignee: NetApp, Inc.
• Inventors: Eslami Sarab, Farshid
• Granted Patent: US 9,842,026 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1435 using file system or storage system metadata
• CPC Class Codes: G06F 11/1446 Point-in-time backing up or restoration of persistent data
• CPC Class Codes: G06F 11/1448 Management of the data involved in backup or backup restore
• CPC Class Codes: G06F 2201/82 Solving problems relating to consistency
• CPC Class Codes: G06F 2201/84 Using snapshots, i.e. a logical point-in-time copy of the data

Abstract

Various of the disclosed embodiments provide for recovery following inadvertent errors in a Log-Structured File System (LSFS). Particularly, embodiments mitigate inadvertent errors introduced by a file system consistency check operation by creating file system images at an appropriate time. The images may be stored within the portion of the file system accessible to a user. The images may be created in conjunction with the mounting of the file system and in such a fashion as to preserve the file system data should an error occur. Restoring the system to one of the images may remove any errors introduced by the consistency check, or similar, operation.

Claims

1. A computer-implemented method for creating a snapshot in a Log-Structured File System (LSFS), comprising:

disabling automatic consistency checkpoint creation for the LSFS;

performing at least one precondition check;

mounting a superblock;

creating an image of at least a portion of the superblock in a region of LSFS memory accessible to a user; and

making the at least the portion of the LSFS available for verification.

2. The computer-implemented method of claim 1, wherein creating an image of at least a portion of the superblock in a region of LSFS memory accessible to a user comprises re-reading an active map associated with the superblock from disk.

3. The computer-implemented method of claim 1, wherein performing at least one precondition check comprises performing at least one of checking for a valid volume type, checking for available free disk space, and checking for the existence of a snapshot.

4. The computer-implemented method of claim 1, further comprising removing a pre-check snapshot.

5. The computer-implemented method of claim 1, further comprising:

disabling write operations to storage devices associated with the region of LSFS memory accessible to a user prior to storing the image within the active file system; and

enabling write operations to storage devices associated with the region of LSFS memory accessible to a user subsequent to storing the image within the active file system.

6. The computer-implemented method of claim 1, wherein creating an image of at least a portion of the superblock in a region of LSFS memory accessible to a user comprises:

identifying free memory for a snapshot;

copying a block number of the active file system to the free memory;

establishing a snapshot-related inode in memory based on an AFS activemap.

7. The computer-implemented method of claim 6, wherein the activemap is the activemap of the AFS currently in memory.

8. A computer system in communication with an Log-Structured File System (LSFS), comprising:

at least one processor;

at least one memory storing instructions, the instructions executable by the at least one processor to;

disable automatic consistency checkpoint creation for the LSFS;

perform at least one precondition check;

mount a superblock;

create an image of at least a portion of the superblock in a region of LSFS memory accessible to a user; and

make the at least a portion of the LSFS available for verification.

9. The computer system of claim 8, wherein creating an image of at least a portion of the superblock in a region of LSFS memory accessible to a user comprises re-reading an active map associated with the superblock from disk.

10. The computer system of claim 8, wherein performing at least one precondition check comprises performing at least one of checking for a valid volume type, checking for available free disk space, and checking for the existence of a snapshot.

11. The computer system of claim 8, the instructions further executable by the at least one processor to remove a pre-check snapshot.

12. The computer system of claim 8, the instructions further executable by the at least one processor to:

disable write operations to storage devices associated with the region of LSFS memory accessible to a user prior to storing the image within the active file system; and

enable write operations to storage devices associated with the region of LSFS memory accessible to a user subsequent to storing the image within the active file system.

13. The computer system of claim 8, wherein creating an image of at least a portion of the superblock in a region of LSFS memory accessible to a user comprises:

identifying free memory for a snapshot;

copying a block number of the active file system to the free memory;

establishing a snapshot-related inode in memory based on an AFS activemap.

14. The computer system of claim 13, wherein the activemap is the activemap of the AFS currently in memory.

15. A non-transitory computer-readable storage comprising instructions executable by at least one processor to:

disable automatic consistency checkpoint creation for an Log-Structured File System (LSFS);

perform at least one precondition check;

mount a superblock;

create an image of at least a portion of the superblock in a region of LSFS memory accessible to a user; and

make the at least a portion of the LSFS available for verification.

16. The non-transitory computer-readable storage of claim 15, wherein creating an image of at least a portion of the superblock in a region of LSFS memory accessible to a user comprises re-reading an active map associated with the superblock from disk.

17. The non-transitory computer-readable storage of claim 15, wherein performing at least one precondition check comprises performing at least one of checking for a valid volume type, checking for available free disk space, and checking for the existence of a snapshot.

18. The non-transitory computer-readable storage of claim 15, the instructions further executable by at least one processor to remove a pre-check snapshot.

19. The non-transitory computer-readable storage of claim 15, the instructions further executable by at least one processor to:

disable write operations to storage devices associated with the region of LSFS memory accessible to a user prior to storing the image within the active file system; and

enable write operations to storage devices associated with the region of LSFS memory accessible to a user subsequent to storing the image within the active file system.

20. The non-transitory computer-readable storage of claim 15, wherein creating an image of at least a portion of the superblock in a region of LSFS memory accessible to a user comprises:

identifying free memory for a snapshot;

copying a block number of the active file system to the free memory;

establishing a snapshot-related inode in memory based on an AFS activemap.

21. The non-transitory computer-readable storage of claim 20, wherein the activemap is the activemap of the AFS currently in memory.