Virtualization of file input/output operations

• US 9,262,433 B2
• Filed: 11/11/2014
• Issued: 02/16/2016
• Est. Priority Date: 12/29/2006
• Status: Active Grant

• Current Assignee: Veritas Technologies, LLC (Whitehouse Group Ltd.)
• Original Assignee: Symantec Operating Corporation (NortonLifeLock Inc.)
• Inventors: Searls, Kirk L., Dickinson, Derek
• Primary Examiner(s): Woo, Isaac M
• Application Number:
  US14/538,439
• Publication Number:
  US 20150067706A1
• Time in Patent Office: 462 Days
• Field of Search: 707600-899
• US Class Current: 1/1
• CPC Class Codes: G06F 16/00 Information retrieval; Database structures therefor; File system structures therefor
• CPC Class Codes: G06F 16/16 File or folder operations, e.g. details of user interfaces specifically adapted to file systems
• CPC Class Codes: G06F 16/1756 based on delta files
• CPC Class Codes: G06F 16/188 Virtual file systems
• CPC Class Codes: G06F 16/219 Managing data history or versioning querying versioned data G06F16/2474; querying temporal data G06F16/2477
• CPC Class Codes: G06F 9/54 Interprogram communication

Abstract

Various embodiments of a system and method for providing input/output virtualization for a file are disclosed. The system may include a filter program that intercepts a write request for a particular file and stores change information specifying the data and the write location indicated by the write request. However, the file itself is not modified. The filter program may also intercept a read request referencing the file and determine whether change information representing a write request to write data at the location specified by the read request has been previously stored. If so then the data specified by the change information is returned in response to the read request.

Claims

1. A method, comprising:

intercepting a read request for a file by a filter program, wherein the read request includes a location in the file from which to read;

searching, by the filter program, for change information related to the file in response to determining that access requests for the file are to be redirected to a change database; and

sending data specified in the change information by the filter program to an application program in response to finding the change information related the file, wherein the change information is indicative of a previous change to the file.

2. The method of claim 1, further comprising forwarding the read request to file system software in response to determining access requests for the file are to be performed directly on the file.

3. The method of claim 1, further comprising forwarding the read request to file system software in response to determining responsive to determining the change information related to the file is not available.

4. The method of claim 1, wherein the change database includes a delta file, and wherein searching, by the filter program, for the change information related to the file includes reading the delta file, wherein the delta file includes pending changes for the file.

5. The method of claim 1, wherein the read request for the file includes a read request for a first portion of the file, and a read request for a second portion of the file.

6. The method of claim 5, wherein sending the data specified in the change information comprises reading the second portion of the file directly from the file in response to determining the second portion of the file has not changed.

7. A non-transitory computer-accessible storage medium having program instructions store therein that, in response to execution by a processor, cause the processor to perform operations comprising:

intercepting a read request for a file, wherein the read request includes a location in the file from which to read;

searching for change information related to the file in response to determining that access requests for the file are to be redirected to a change database; and

sending data specified in the change information to an application program in response to finding the change information related to the file, and wherein the change information is indicative of a previous change the file.

8. The non-transitory computer-accessible storage medium of claim 7, wherein the operations further comprise forwarding the read request to file system software in response to determining access requests for the file are to be performed directly on the file.

9. The non-transitory computer-accessible storage medium of claim 7, wherein the operations further comprise forwarding the read request to file system software responsive to determining in response to determining the change information is not available.

10. The non-transitory computer-accessible storage medium of claim 7, wherein the change database includes a delta file, and wherein searching for the change information related to the file comprises reading the delta file, wherein the delta file includes pending changes for the file.

11. The non-transitory computer-accessible storage medium of claim 7, wherein the location in the file from which to read includes an offset from a beginning of the file.

12. The non-transitory computer-accessible storage medium of claim 7, wherein the read request for the file includes a read request for a first portion of the file, and a read request for a second portion of the file.

13. The non-transitory computer-accessible storage medium of claim 12, wherein sending the data specified in the change information comprises reading the second portion of the file from an original copy in response to determining the second portion of the file has not changed.

14. A system, comprising:

a processor; and

a memory medium storing program instruction;

wherein the processor is operable to execute the program instructions to;

intercept a read request for a file, wherein the read request includes a location in the file from which to read;

search for change information related to the file in response to determining that access requests for the file are to be redirected to a change database; and

send data specified in the change information to an application program in response to finding the change information related to the file, and wherein the change information is indicative of a previous change the file.

15. The system of claim 14, wherein the processor is further operable to execute the program instructions to forward the read request to file system software in response to determining access requests for the file are to be performed directly on the file.

16. The system of claim 14, wherein the operations further comprise forwarding the read request to file system software in response to determining responsive to determining the change information is not available.

17. The system of claim 14, wherein to search for the change information related to the file, the processor is further configured to execute program instructions to reading a delta file, wherein the delta file includes pending changes for the file.

18. The system of claim 14, wherein the location in the file from which to read includes an offset from a beginning of the file.

19. The system of claim 14, wherein the change information includes information indicative of a version of the file.

20. The system of claim 14, wherein to intercept the read request for the file, the processor is further operable to execute the program instructions to detect the application program calling an Application Programming Interface (API) of file system software.