Systems and methods for a snapshot of data

• US 8,356,013 B2
• Filed: 12/17/2010
• Issued: 01/15/2013
• 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: Fachan, Neal T., Husted, Justin M., Lemar, Eric M., Schack, Darren P.
• Primary Examiner(s): Moser, Bruce
• Application Number:
  US12/972,260
• Publication Number:
  US 20110087635A1
• Time in Patent Office: 760 Days
• Field of Search: 707/203, 707/204, 707/999.203, 707/999.204, 707/648, 707/649, 707/100, 707/102, 707/999.1, 707/999.102
• US Class Current: 707/648
• 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

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. In an embodiment, a snapshot tracking data structure is maintained for efficient creation and deletion of the snapshot.

Claims

1. A data storage system configured to efficiently create and delete snapshots of files and directories, the system comprising:

at least one storage device;

at least one computer processor; and

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

create a first snapshot of data stored on the at least one storage device, wherein the data comprises one or more files or directories;

obtain a request to modify one or more portions of the data;

responsive to the request to modify one or more portions of the data, create a snapshot tracking data structure associated with the first snapshot of data, wherein the snapshot tracking data structure is configured to store references associated with the one or more portions of the data; and

delete the first snapshot, wherein deleting the first snapshot includes;

determining whether each of the one or more portions of the data is governed by an earlier snapshot than the first snapshot;

responsive to determining that a first portion of the one or more portions of data is governed by the earlier snapshot, determining whether the first portion of the data has been modified; and

responsive to determining that the first portion of the data has been modified, replacing a pointer in the earlier snapshot that points to a reference in the first snapshot that points to a location on the at least one storage device where the first portion of data is store with a direct reference to the location.

2. The data storage system of claim 1, wherein the at least one executable software module is further configured to create a snapshot tracking data structure each time a snapshot is created.

3. The data storage system of claim 1, wherein the at least one executable software module is further configured to delete the snapshot tracking data structure after deleting the first snapshot.

4. The data storage system of claim 1, wherein deleting the first snapshot comprises deleting metadata associated with the first snapshot.

5. The data storage system of claim 1, wherein the references associated with the one or more portions of the data are references to metadata associated with the one or more portions of the data.

6. The data storage system of claim 1, wherein the snapshot tracking data structure is further configured to store references associated with one or more portions of the data, wherein the one or more portions of the data have been read after the first snapshot is created.

7. The data storage system of claim 1, wherein the snapshot tracking data structure is further configured to store references associated with one or more portions of the data, wherein the one or more portions of the data have been read after the first snapshot is created and before a subsequent snapshot is created.

8. The data storage system of claim 1, wherein the at least one executable software module is further configured to create a table, wherein the table is configured to store a plurality of references pairs, each reference pair comprising a first reference associated with a portion of data stored on the at least one storage device and a second reference associated with a snapshot governing that portion of data.

9. The data storage system of claim 8, wherein the at least one executable software module is further configured to determine whether there is an earlier snapshot governing the associated portion by checking the table for a reference associated with the associated portion.

10. The data storage system of claim 8, wherein the first reference is a reference to metadata associated with the portion of data.

11. A method for efficiently creating and deleting snapshots of files and directories, the method comprising:

creating, by one or more computer processors, a first snapshot of data stored on the at least one storage device, wherein the data comprises one or more files or directories;

obtaining, by one or more computer processors, a request to modify one or more portions of the data;

responsive to the request to modify one or more portions of the data creating, by one or more computer processors, a snapshot tracking data structure associated with the first snapshot of data, wherein the snapshot tracking data structure is configured to store references associated with the one or more portions of the data; and

deleting, by one or more computer processors, the first snapshot, wherein deleting the first snapshot includes;

determining whether each of the one or more portions of the data is governed by an earlier snapshot than the first snapshot;

responsive to determining that a first portion of the one or more portions of data is governed by the earlier snapshot, determining whether the first portion of the data has been modified; and

responsive to determining that the first portion of the data has been modified, replacing a pointer in the earlier snapshot that points to a reference in the first snapshot that points to a location on the at least one storage device where the first portion of data is stored with a direct reference to the location.

12. The method of claim 11, further comprising creating a snapshot tracking data structure each time a snapshot is created.

13. The method of claim 11, further comprising deleting the snapshot tracking data structure after deleting the first snapshot.

14. The method of claim 11, wherein deleting the first snapshot comprises deleting metadata associated with the first snapshot.

15. The method of claim 11, wherein the references associated with the one or more portions of the data are references to metadata associated with the one or more portions of the data.

16. The method of claim 11, wherein the snapshot tracking data structure is further configured to store references associated with one or more portions of the data, wherein the one or more portions of the data have been read after the first snapshot is created.

17. The method of claim 11, wherein the snapshot tracking data structure is further configured to store references associated with one or more portions of the data, wherein the one or more portions of the data have been read after the first snapshot is created and before a subsequent snapshot is created.

18. The method of claim 11, further comprising creating a table, wherein the table is configured to store a plurality of references pairs, each reference pair comprising a first reference associated with a portion of data stored on the at least one storage device and a second reference associated with a snapshot governing that portion of data.

19. The method of claim 18, further comprising determining whether there is an earlier snapshot governing the associated portion by checking the table for a reference associated with the associated portion.

20. The method of claim 18, wherein the first reference is a reference to metadata associated with the portion of data.