Providing a snapshot of a subject of a file system

• US 7,111,014 B2
• Filed: 10/15/2004
• Issued: 09/19/2006
• Est. Priority Date: 02/15/2002
• Status: Expired due to Term

• Current Assignee: SAP SE
• Original Assignee: International Business Machines Corporation
• Inventors: Sawdon, Wayne A., Schmuck, Frank B.
• Primary Examiner(s): Alam, Shahid
• Application Number:
  US10/966,870
• Publication Number:
  US 20050050110A1
• Time in Patent Office: 704 Days
• Field of Search: 707/10, 707/202, 707/203, 707/204, 707/9, 707/201, 707/205, 707/102, 711/4, 711/111, 711/114, 714/4, 714/6, 709/201, 717/11
• US Class Current: 1/1
• 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 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 allocated to a file or directory that is part of the desired snapshot;

restoring, in response to determining that the corresponding inode in the file system is allocated to a file or directory that is part of the desired snapshot, the inode in the desired snapshot to the corresponding inode in the file system;

restoring, in response to determining that the corresponding inode in the file system is not allocated to a file or directory that is not part of the desired snapshot, the inode in the desired snapshot to an unallocated inode in the file system; and

updating and providing a directory entry for the corresponding inode in the file system to reference the previously unallocated inode.

4. The method of claim 1, wherein the determining whether a corresponding inode in a file system is allocated to a file or directory that is part of the desired snap shot comprises determining if the corresponding inode is 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.

2. 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;

restoring, in response to determining that the corresponding inode in the file system is available, the inode in the desired snapshot to the corresponding inode in the file system;

restoring, in response to determining that the corresponding inode in the file system is not available, the inode in the desired snapshot to an unallocated inode in the file system; and

updating and providing a directory entry for the corresponding inode in the file system to reference the previously unallocated inode.

5. The computer readable medium of claim 2, wherein the computer instructions for determining whether a corresponding inode in a file system is allocated to a file or directory that is part of the desired snapshot comprises computer instructions for determining if the corresponding inode is 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.

3. 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, operating in response to a determination by the means for determining that the corresponding inode in the file system is available, the inode in the desired snapshot to the corresponding inode in the file system;

means for restoring, operating in response to a determination by the means for determining that the corresponding inode in the file system is not available, the inode in the desired snapshot to an unallocated inode in the file system; and

means for updating and means for providing a directory entry for the corresponding inode in the file system to reference the previously unallocated inode.

6. The system of claim 3, wherein the means for determining whether a corresponding inode in a file system is allocated to a file or directory that is part of the desired snapshot comprises determining if the corresponding inode is 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.