SYSTEMS AND METHODS FOR A SNAPSHOT OF DATA

• US 20100161557A1
• Filed: 03/04/2010
• Published: 06/24/2010
• Est. Priority Date: 08/18/2006
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Husted, Justin M., Schack, Darren P., Passey, Aaron J., Lemar, Eric M., Anderson, Robert J., Fachan, Neal T.
• Granted Patent: US 8,015,156 B2
• Time in Patent Office: Days
• US Class Current: 707/638
• CPC Class Codes: G06F 16/128 Details of file system snapshots on the file-level, e.g. snapshot creation, administration, deletion use of snapshots for error detection or correction G06F11/14, G06F11/16
• 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: Y10S 707/99953 Recoverability

Abstract

In one embodiment, a user or client device is connected to a distributed file system comprised of one or more physical nodes. The data on each of the physical nodes store metadata about files and directories within the file system. Some of the embodiments permit a user to take a snapshot of data stored on the file system. The snapshot may include a single file, a single directory, a plurality of files within a directory, a plurality of directories, a path on the file system that includes nested files and subdirectories, or more than one path on the file system that each includes nested files and directories. According to one embodiment, the system stores representations of the snapshots that govern a file or directory and its descendants within metadata associated with that file or directory. In one embodiment, before modifying a file or directory, the system updates the representations of the governing snapshots by traversing the metadata of ancestors of the file or directory.

Claims

1. A system for preserving access to previous versions of directories and files stored in a processor-accessible storage system, the system comprising:

at least one memory;

at least one computer processor;

a plurality of metadata structures logically arranged in a hierarchical structure and stored on the at least one memory, each metadata structure corresponding to a file or directory of a file system and comprising a governance list, the governance list configured to store two or more snapshot identifiers, each snapshot identifier identifying a snapshot governing the corresponding file or directory; and

at least one executable software module executed by the at least one computer processor and configured to;

access a governance list of at least one ancestor metadata structure of a target metadata structure corresponding to a target file or directory; and

determine if the target file or directory is governed by one or more snapshots based on the accessed governance list of at least one ancestor metadata structure.

2. The system of claim 1, wherein the at least one executable software module is further configured to, if it determines that the target file or directory is governed by one or more snapshots, add a snapshot identifier to the governance list of the target metadata structure for each of the one or more snapshots which are not already identified in the governance list of the target metadata structure.

3. The system of claim 2, wherein the at least one executable software module is further configured to:

access an additional at least one ancestor metadata structure of the target metadata structure;

determine if a file or directory corresponding to the additional at least one ancestor metadata structure is governed by one or more snapshots based on the accessed governance list of the at least one ancestor metadata structure; and

if it determines that a file or directory corresponding to the additional at least one ancestor metadata structure is governed by one or more snapshots, add a snapshot identifier to the governance list of the additional at least one ancestor metadata structure for each of the one or more snapshots which are not already identified in the governance list of the additional at least one ancestor metadata structure.

4. The system of claim 1, wherein the at least one executable software module is further configured to:

receive a request to modify the target file or directory; and

modify the target file or directory.

5. The system of claim 4, wherein the at least one executable software module is configured to determine if the target file or directory is governed by one or more snapshots after the target file or directory is modified.

6. The system of claim 5, wherein the at least one executable software module is configured to determine if the target file or directory is governed by one or more snapshots as a result of the request to modify the target file or directory.

7. The system of claim 4, wherein the at least one executable software module is configured to determine if the target file or directory is governed by one or more snapshots before the target file or directory is modified.

8. The system of claim 7, wherein the at least one executable software module is configured to determine if the target file or directory is governed by one or more snapshots as a result of the request to modify the target file or directory.

9. The system of claim 1, wherein the at least one executable software module is further configured to:

receive a request to create a snapshot of a file or directory with one or more descendants;

create a snapshot of the file or directory and its one or more descendants; and

as a result of the request to create a snapshot, add an identifier of the snapshot to the governance list of the metadata structure corresponding to the file or directory but not to the governance lists of metadata structures corresponding to the one or more descendants of the file or directory.

10. The system of claim 1, wherein the at least one executable software module is capable of accessing the governance list of every ancestor metadata structure of the target metadata structure.

11. A method of preserving access to previous versions of directories and files stored in a processor-accessible storage system, the method comprising:

providing a plurality of metadata structures logically arranged in a hierarchical structure on at least one memory, each metadata structure corresponding to a file or directory of a file system and comprising a governance list, the governance list configured to store two or more snapshot identifiers, each snapshot identifier identifying a snapshot governing the corresponding file or directory;

accessing, by a computer processor, a governance list of at least one ancestor metadata structure of a target metadata structure corresponding to a target file or directory; and

determining, by the computer processor, if the target file or directory is governed by one or more snapshots based on the accessed governance list of at least one ancestor metadata structure.

12. The method of claim 11, further comprising, if it is determined that the target file or directory is governed by one or more snapshots, adding a snapshot identifier to the governance list of the target metadata structure for each of the one or more snapshots which are not already identified in the governance list of the target metadata structure.

13. The method of claim 12, wherein the accessing comprises:

accessing an additional at least one ancestor metadata structure of the target metadata structure;

determining if a file or directory corresponding to the additional at least one ancestor metadata structure is governed by one or more snapshots based on the accessed governance list of the at least one ancestor metadata structure; and

if it is determined that a file or directory corresponding to the additional at least one ancestor metadata structure is governed by one or more snapshots, adding a snapshot identifier to the governance list of the additional at least one ancestor metadata structure for each of the one or more snapshots which are not already identified in the governance list of the additional at least one ancestor metadata structure.

14. The method of claim 11, further comprising:

receiving a request to modify the target file or directory; and

modifying the target file or directory.

15. The method of claim 14, wherein the determining is performed after the target file or directory is modified.

16. The method of claim 15, wherein the determining is performed as a result of the request to modify the target file or directory.

17. The method of claim 14, wherein the determining is performed before the target file or directory is modified.

18. The method of claim 17, wherein the determining is performed as a result of the request to modify the target file or directory.

19. The method of claim 11, further comprising:

receiving a request to create a snapshot of a file or directory with one or more descendants;

creating a snapshot of the file or directory and its one or more descendants; and

as a result of the request to create a snapshot, adding an identifier of the snapshot to the governance list of the metadata structure corresponding to the file or directory but not to the governance lists of metadata structures corresponding to the one or more descendants of the file or directory.

20. The method of claim 11, further comprising accessing the governance list of every ancestor metadata structure of the target metadata structure.