System and method for reducing storage requirement in backup subsystems utilizing segmented compression and differencing

• US 5,813,017 A
• Filed: 09/03/1996
• Issued: 09/22/1998
• Est. Priority Date: 10/24/1994
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Morris, Robert J. T.
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): Choules, Jack M.
• Application Number:
  US08/707,263
• Time in Patent Office: 749 Days
• Field of Search: 707/200, 707/202, 707/203, 707/204
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1451 by selection of backup contents
• CPC Class Codes: G06F 11/1464 for networked environments
• CPC Class Codes: G06F 16/10 File systems; File servers
• CPC Class Codes: Y10S 707/99931 Database or file accessing
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99955 Archiving or backup

Abstract

In a client/server environment, a method and means for reducing the storage requirement in the backup subsystem and further reducing the load on the transmission bandwidth where base files are maintained on the server in a segmented compressed format. When a file is modified on the client, the file is transmitted to the server and compared with the segmented compressed base version of the file utilizing a differencing function but without decompressing the entire base file. A delta file which is the difference between the compressed base file and the modified version of the file is created and stored on a storage medium which is part of the backup subsystem. Alternatively, a copy of frequently accessed base files are maintained on the client in a compressed format. Whenever the client detects that a frequently accessed file has been modified, the modified version of the file is differenced against the base version of that file without decompressing the entire base file and a delta file is generated. The delta file is then transmitted to the server to be stored at the server for storage medium to be utilized either immediately or at a later time to update the base version of the modified file on the server.

Claims

1. A method for storing information in a client-server environment having a client and a backup subsystem, the backup subsystem comprising a backup server, a server backup program, a storage medium, and a copy of a versioned sequence of a file stored in the storage medium, said versioned sequence comprising a base version of a file in multiple compressed segments and a predetermined number of delta files, the client having a client backup program and a storage medium, the client and the backup server are connected to each other by a communication link, comprising the steps of:

establishing a backup session between the client and the backup server;

detecting, using the client backup program, a changed version of said file at the client;

transmitting said changed version of said file, using the communication link, from the client to the backup subsystem; and

differencing, using the backup subsystem, the changed version of said file and the base version of said file to create a delta file.

2. A method as recited in claim 1 further including the step of:

consulting a backup catalog at the backup subsystem to locate the versioned sequence of said file before differencing.

3. A method as recited in claim 2 further including the steps of:

deleting the base version of said file in the backup subsystem after differencing;

storing said delta file in the storage medium of the backup subsystem; and

storing the changed version of said file as the new base version of said file on the storage medium of the backup subsystem.

4. A method as recited in claim 3 further including the step of deleting the oldest delta file in said versioned sequence of said file after storing the new base version of said file in the backup subsystem.

5. A method as recited in claim 3 wherein the changed version of said file is stored in a form of a multiple compressed segments.

6. A method as recited in claim 1 wherein the step of establishing a backup session comprises the steps of:

transmitting a query, using the communication link, to the client by the backup subsystem; and

receiving a backup session established signal, using the communication link, from the client by the backup subsystem.

7. A method as recited in claim 1 wherein said communication link is a transmission line.

8. A method as recited in claim 1 wherein said backup server is a personal computer.

9. A method as recited in claim 1 wherein said backup server is a workstation.

10. A method as recited in claim 1 wherein said backup subsystem storage medium comprises a magnetic storage device.

11. A method as recited in claim 1 wherein said backup subsystem storage medium comprises an optical storage device.

12. A method as recited in claim 1 wherein said backup subsystem storage medium comprises a tape storage device.

13. A method as recited in claim 1 wherein the step of transmitting a changed version of said file further includes transmitting the changed version of said file in an uncompressed format.

14. A method as recited in claim 13 wherein the step of differencing, using the backup subsystem, is further carried out using the multiple compressed segments of the base version of said file and the changed version of said file.

15. A method as recited in claim 1 wherein the step of transmitting the changed version of said file comprises the step of transmitting the multiple compressed segments of the changed version of said file one compressed segment at a time.

16. A method as recited in claim 15 further including the steps of:

transmitting, using said communication link, a side file to the client from the backup subsystem; and

utilizing, using client computer, said side file for compressing the changed version of said file into multiple compressed segments.

17. A method for storing and transmitting information in a client-server environment having a client and a backup subsystem, the backup subsystem comprising a backup server, a server backup program, a storage medium, and a copy of a versioned sequence of a file stored in the storage medium, said versioned sequence comprising a base version of a file in multiple compressed segments and a predetermined number of delta files, the client and the server are in communication with each other by a communication link, comprising the steps of:

establishing a backup session between the client and the backup subsystem;

detecting a changed version of said file at the client;

differencing, using the client, the changed version of said file and the base version of said file at the client to create a delta file;

transmitting said delta file, using the communication link, to the backup subsystem; and

storing said delta file in the backup subsystem.

18. A method as recited in claim 17 further including the steps of:

generating the changed version of said file at the backup subsystem using said delta file and the base version of said file; and

storing the changed version of said file as the new base version of said file in the backup subsystem.

19. A method as recited in claim 18 further including the step of deleting the base version of said file at the backup subsystem after generating the changed version of said file at the backup subsystem.

20. A method as recited in claim 17 wherein the step of differencing at the client further includes the steps of:

checking the storage medium at the client to determine if a copy of the base version of said file is available in the client storage medium;

requesting a copy of the base version of said file from the backup subsystem if a copy of the base version of said file is not available in the client storage medium; and

receiving a copy of the base version of said file from the backup subsystem if a copy of the base version of said file is not available in the client storage medium.

21. A method as recited in claim 20 wherein the client storage medium is a cache.

22. A method as recited in claim 20 where a copy of the base version of said file is stored at the client storage medium in a multiple compressed segments.

23. A method as recited in claim 17 wherein the step of differencing, using the client, is further carried out using the multiple compressed segments of the base version of said file and the changed version of said file.

24. A method as recited in claim 17 wherein said communication link is a transmission line.

25. A method as recited in claim 17 wherein said backup server is a personal computer.

26. A method as recited in claim 17 wherein said backup server is a workstation.

27. A method as recited in claim 17 wherein said backup subsystem storage medium comprises a magnetic storage device.

28. A method as recited in claim 17 wherein said backup subsystem storage medium comprises an optical storage device.

29. A method as recited in claim 17 wherein said backup subsystem storage medium comprises a tape storage device.

30. In a client-server environment having a client and a backup subsystem, the backup subsystem comprising a backup server and a backup storage medium, and where the client comprises a client storage medium, the client and the backup server connected to each other by a communication link, a method for storing and transmitting information in said client-server environment, comprising the steps of:

storing a versioned sequence of a file, using the backup storage medium, in the backup subsystem, said versioned sequence comprising a base version of a file in multiple compressed segments and a predetermined number of delta files;

detecting a changed version of said file at the client;

differencing, using the client, the changed version of the said file and the base version of said file to create a delta file at the client;

transmitting, using the communication link, said delta file to the server; and

storing said delta file in the backup subsystem.

31. A method as recited in claim 30 further including the steps of:

creating a changed version of said file at the backup subsystem using said delta file and the base version of said file;

storing the changed version of said file at the backup subsystem; and

deleting the base version of said file from the backup subsystem.

32. A method as recited in claim 31 wherein the step of storing the changed version of said file includes storing multiple compressed segments of said file.

33. A method as recited in claim 30 wherein the step of differencing, using the client, is carried out using the multiple compressed segments of the base version of said file and the changed version of said file.

34. A method as recited in claim 30 further including the step of storing the copy of the base version of said file in the client storage medium according to an established qualification criteria.

35. A method as recited in claim 30 further including the step of storing the changed version of the file in the client at the completion of comparing the changed version of said file and the base version of said file.

36. A method as recited in claim 30 further including the step of updating the base version of said file at a predetermined time.

37. In a client-server environment having a client and a backup subsystem, the backup subsystem comprising a backup server and a storage medium, the client is connected to the backup server by a communication link, the backup subsystem including a copy of a versioned sequence of a file, said versioned sequence comprising a base file in a multiple compressed segments and a predetermined number of delta files, said client-server environment comprising:

means for establishing a backup session between the client and the backup server;

means for transmitting a changed version of said file, from the client to the backup subsystem;

means for differencing, the changed version of said file and the base version of said file to create a delta file; and

means for storing said delta file in the backup subsystem.

38. A system as recited in claim 37, further comprising:

means for deleting the base version of said file in the backup subsystem after differencing; and

means for storing the changed version of said file as the new base version of said file on the storage medium of the backup subsystem.

39. In a client-server environment having a client and a backup subsystem, the backup subsystem comprising a backup server and a storage medium, and where the client comprises a client storage medium, the client and the server connected to each other by a communication link, said client-server environment comprising:

means for storing a versioned sequence of a file in the backup subsystem, said versioned sequence comprising a base version of a file in a multiple compressed segments and a predetermined number of delta files;

means for storing a copy of the base version of said file in the client;

means for detecting a changed version of said file at the client;

means for differencing the changed version of said file and the base version of said file to create a delta file at the client;

means for transmitting the delta file to the backup subsystem; and

means for storing said delta file in the backup subsystem so the base version of said file can be updated at a predetermined time.

40. A system as defined in claim 39 further comprising:

means for creating a changed version of said file at the backup subsystem using said delta file and the base version of said file;

means for storing the changed version of said file at the backup server; and

means for deleting the base version of said file at the backup server.

41. A system as defined in claim 39 wherein the means for differencing the base version of said file with the changed version of said file comprises the means for differencing the multiple compressed segments of the base version of said file and the changed version of said file.

42. A method for storing information in a client-server environment having a client and a backup subsystem, the backup subsystem comprising a backup server and a copy of a versioned sequence of a file, said versioned sequence comprising a base version of said file in multiple compressed segments and a predetermined number of delta files, the client and the backup server are in communication with each other, comprising the steps of:

detecting, using the client, a changed version of said file at the client;

transmitting said changed version of said file from the client to the backup subsystem; and

differencing, using the backup subsystem, the changed version of said file and the base version of said file to create a delta file.