SYSTEM AND METHOD FOR STORING REDUNDANT INFORMATION

• US 20080243958A1
• Filed: 03/28/2008
• Published: 10/02/2008
• Est. Priority Date: 12/22/2006
• Status: Active Grant

• Current Assignee: CommVault Systems Incorporated
• Original Assignee: CommVault Systems Incorporated
• Inventors: Gokhale, Parag, Attarde, Deepak R., Prahlad, Anand, Kottomtharayil, Rajiv, Vijayan Retnamma, Manoj K.
• Granted Patent: US 8,037,028 B2
• Time in Patent Office: Days
• US Class Current: 707/204
• CPC Class Codes: G06F 11/1453 using de-duplication of the data
• CPC Class Codes: G06F 16/1748 De-duplication implemented within the file system, e.g. based on file segments de-duplication techniques in storage systems for the management of data blocks G06F3/0641
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0638 Organizing or formatting or addressing of data
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]
• CPC Class Codes: G11B 5/86 Re-recording, i.e. transcribing information from one magnetisable record carrier on to one or more similar or dissimilar record carriers by varying the order of the information G11B27/029, G11B27/036

Abstract

A method and system for reducing storage requirements and speeding up storage operations by reducing the storage of redundant data includes receiving a request that identifies one or more data objects to which to apply a storage operation. For each data object, the storage system determines if the data object contains data that matches another data object to which the storage operation was previously applied. If the data objects do not match, then the storage system performs the storage operation in a usual manner. However, if the data objects do match, then the storage system may avoid performing the storage operation.

Claims

1. A method in a computer system for restoring data from a single-instanced copy, the method comprising:

receiving a request to restore one or more data objects originally located within a hierarchy to a destination location, wherein the copy of data contains information describing the hierarchy, but only contains a single instance of each data object with the hierarchy flattened for storage on sequential media, and wherein the request specifies the original location within the hierarchy of the data objects to be restored;

for each data object in the request;

determining whether the data at the original location within the hierarchy specified by the request contains a reference to a data object or the data object itself;

if the original location within the hierarchy specified by the request contains a reference to a data object, resolving the reference to find the actual data object and copying the data object to the destination location; and

if the original location within the hierarchy specified by the request contains the data object itself, copying the data object to the destination location.

2. The method of claim 1 wherein the hierarchy is a file system hierarchy, and wherein the copy of data contains a single instance of the data of each file in the file system hierarchy, and wherein additional instances of each file in the original location are stored as stubs within the copy of data that reference the single instance of the data of each file.

3. The method of claim 1 wherein the reference contains a pointer to the location of the actual data for the data object, and wherein resolving the reference comprises locating the actual data based on the pointer.

4. The method of claim 1 wherein the one or more data objects are email messages and wherein the hierarchy comprises folders within an email message store.

5. The method of claim 1 wherein the copy of data is stored on one or more sequential media, wherein the reference contains a media identifier and offset of the actual data object, and wherein resolving the reference comprises locating the media identified by the media identifier and seeking to the offset.

6. The method of claim 1 wherein the copying the data object to the destination location further comprises decrypting the data object.

7. A system for restoring single instanced data from sequential media, the system comprising:

a file identification component configured to identify one or more files stored on the sequential media based on an original location of the file;

a restored file cache configured to receive copies of files from the sequential media; and

a storage operation manager configured to;

receive requests to restore a file stored on the sequential media, wherein each file stored on the sequential media contains a location based on the original location of the file,

traverse the sequential media and restore any instances of the file encountered to the restored file cache at the location based on the original location of the file, and

when an encountered instance references an earlier instance of the file, copy the data from the location of the earlier instance in the restored file cache to the location associated with the encountered instance in the restored file cache.

8. The system of claim 7 including a single instance database component that contains an index identifying the location of each file tracked by the system.

9. The system of claim 7 wherein the file identification component identifies a file by associating a path representing the original location of the file with a media identifier and offset that specify a unique location on the sequential media.

10. The system of claim 7 wherein the sequential media is magnetic tape and wherein the restored file cache uses random access media.

11. The system of claim 7 wherein the restored file cache is an intermediate holding location for files during a restore operation, and wherein the restored file cache is cleared after the restore operation is complete.

12. The system of claim 7 wherein traversing the sequential media comprises scanning the sequential media from a beginning of the sequential media to the location of the file specified by the request.

13. The system of claim 7 wherein an encountered instance references an earlier instance of the file by containing header information that identifies the encountered instance as a reference and identifies the location on the sequential media of the earlier instance.

14. A computer-readable medium containing instructions for improving the retrieval of a data object in a network environment that contains multiple instances of the data object, by a method comprising:

receiving a request to access the data object at a first location;

determining at least one alternative location of an instance of the requested data object, wherein the at least one alternative location is not the first location;

selecting an instance of the data object from among the determined at least one alternative location to use to satisfy the request; and

sending the selected instance of the data object in response to the request.

15. The computer-readable medium of claim 14 wherein a computer system from which the request is received is closer to the selected alternative location than to the first location.

16. The computer-readable medium of claim 14 wherein the request is an HTTP request for a data object located on the world wide web, and wherein the alternative location is a location within a private local area network.

17. The computer-readable medium of claim 14 wherein the request contains a digest value for identifying the data object, and wherein determining the at least one alternative location of an instance of the requested data object comprises comparing the digest value to an index of digest values of data objects stored within the network environment.

18. The computer-readable medium of claim 14 wherein selecting an instance of the data object comprises determining the fastest location from which the data object is available.

19. The computer-readable medium of claim 14 wherein selecting an instance of the data object comprises identifying multiple copies containing instances of the data object and determining attributes of each copy that affect an accessing speed for the data object.

20. The computer-readable medium of claim 14 wherein sending the selected instance of the data object comprises copying the data object from the selected alternative location to an intermediate location, and then from the intermediate location to a location specified in the request.