Systems and methods for a snapshot of data

• US 20080046476A1
• Filed: 08/18/2006
• Published: 02/21/2008
• Est. Priority Date: 08/18/2006
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: Isilon Systems Incorporated (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 7,680,836 B2
• Time in Patent Office: Days
• US Class Current: 707/200
• 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.

Claims

1. A method of modifying data in a file stored in a processor accessible storage system while preserving data stored in the file as of a point in time comprising:

locating the desired file within a hierarchical storage structure; and

checking a node at least one level up the hierarchical storage structure leading to the desired file for an indication that data existing in the file prior to modification should be preserved.

2. The method of claim 1 wherein the locating and checking is performed after receiving a request to modify at least a portion of the desired file.

3. The method of claim 1 wherein checking includes determining whether the node at least one level up has an up-to-date snap identifier.

4. The method of claim 1 further comprising checking each node up the hierarchical tree from the desired file until the root is reached.

5. The method of claim 1 further comprising checking the hierarchical tree structure from the desired file by using a virtual hierarchical structure which allows for access to data preservation information

6. A processor accessible data storage system allowing for the preservation of data in a file as of a point in time comprising:

a hierarchical structure for storing data including directory nodes and file nodes; and

an indication that the data in a file should be preserved as of specified point in time stored initially at a node other than the file node.

7. The data storage system of claim 6 wherein the node is an ancestor node.

8. A method of accessing the data stored in a storage system as of a selected point in time comprising:

locating the desired file within an index storage structure using a file identifier and a snapshot identifier; and

checking the index storage structure for the desired file to determine if any information stored in the file has been modified since the selected point in time.

9. The method of claim 8 wherein the file identifier and the snapshot identifier are implemented as a single identifier.

10. A method of tracking files to be traversed, the method comprising:

storing a set of data structures that correspond to a plurality of files that are logically stored in a tree;

tracking a set of snapshots that govern subsets of files in the tree;

receiving an identifier for a first file to be modified; and

determining whether the first file is governed by any of the set of snapshots by traversing at least a portion of the tree.

11. The method of claim 10 wherein determining comprises:

traversing up the tree from the first file to determine whether the ancestor nodes indicate that the first file is governed by any of the set of snapshots; and

if the ancestor node is governed by any of the set of snapshots, updating the corresponding data structures of the node in at least one traversed level to indicate the subset of snapshots that govern the ancestor node.

12. The method of claim 10, wherein the file system is a distributed file system.

13. The method of claim 10, wherein the files include files and directories.

14. A system for tracking snapshots of a file system, the system comprising:

a file structure comprising a plurality of files that are logically stored in a tree;

for each of the plurality of files, a data structure corresponding to each of the files and directories, the data structure comprising an indication of the snapshot data currentness of the data structure;

a modification module configured to receive a request to modify one of the plurality of files; and

an update module configured to update at least one of the data structures to determine whether the at least one data structure is governed by a snapshot.

15. The system of claim 14, wherein the update module is configured:

to begin with the data structure that corresponds to at least one of the plurality of files;

to climb a branch of the at least one of the plurality of files, reviewing the corresponding data structure at each climbed level in the branch, until reaching a data structure that indicates that the snapshot data of the data structure is current; and

from that level, to traverse down the one branch to the leaf node file updating the snapshot data of the corresponding data structures at each traversed level in the branch.

16. The system of claim 14, wherein the file system is a distributed file system.

17. The system of claim 14, wherein the files include files and directories.