Continuous data protection

• US 20070033370A1
• Filed: 08/03/2005
• Published: 02/08/2007
• Est. Priority Date: 08/03/2005
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: XIV Ltd. (International Business Machines Corporation)
• Inventors: Helman, Haim, Zohar, Ofir, Schwartz, Shemer, Revah, Yaron, Cohen, Dror
• Granted Patent: US 7,653,800 B2
• Time in Patent Office: Days
• US Class Current: 711/173
• CPC Class Codes: G06F 11/1435 using file system or storage system metadata
• CPC Class Codes: G06F 21/80 in storage media based on magnetic or optical technology, e.g. disks with sectors preventing unauthorised reproduction or copying of disc-type recordable media G11B20/00

Abstract

A method for continuous data protection in a storage system, including receiving a first write command to write first data to a partition of a logical volume and then generating a first partition descriptor record (PDR) having a first timestamp. The method further includes storing the first data at a first location, associating the first PDR with the first location, and receiving a second write command, subsequent to the first command, to update the first data with second data. Responsively to the second command, a second PDR having a second timestamp is generated. The second data is stored at a second location, and the second PDR is associated with the second location. The method includes generating a pointer between the first PDR and the second PDR, and accessing the first PDR using the pointer in response to a read command indicating a time prior to the second timestamp.

Claims

1. A method for continuous data protection in a data storage system, comprising:

receiving a first write command to write first data to a partition of a logical volume;

in response to the first write command, generating a first partition descriptor record (PDR) having a first timestamp;

storing the first data at a first physical location;

associating the first PDR with the first physical location;

receiving a second write command, subsequent to the first write command, to update the first data with second data;

responsively to the second write command, generating a second PDR having a second timestamp;

storing the second data at a second physical location;

associating the second PDR with the second physical location;

generating a pointer between the first PDR and the second PDR; and

accessing the first PDR using the pointer in response to a read command indicating a time prior to the second timestamp.

2. The method according to claim 1, wherein generating the first PDR comprises associating the partition of the logical volume with the first PDR.

3. The method according to claim 2, wherein generating the second PDR comprises disassociating the partition from the first PDR and associating the partition with the second PDR.

4. The method of claim 2, wherein associating the partition of the logical volume with the first PDR comprises generating a pointer to the first PDR in a partition hash table.

5. The method according to claim 1, and comprising linking the first and second PDRs to each other by a binary tree responsively to one or more write commands subsequent to the first and the second write commands.

6. The method according to claim 5, wherein the binary tree is generated by an Adelson-Velskii and Landis (AVL) method.

7. The method according to claim 1, wherein accessing the first PDR comprises comparing the first timestamp with the time indicated by the read command.

8. The method according to claim 1, wherein accessing the first PDR comprises comparing the first timestamp with the time indicated by the read command and with a predetermined threshold period of time.

9. The method according to claim 1, wherein the first PDR comprises a bitmap field and wherein generating the second PDR comprises using the bitmap field to determine that the first write command and the second write command do not comprise a single split write command.

10. The method according to claim 1, wherein the logical volume comprises a source logical volume, wherein the partition comprises a first partition, the method comprising, responsively to a volume copy command to copy the source logical volume to a target logical volume:

generating a third PDR having the first timestamp;

associating the third PDR with the first physical location; and

associating with the third PDR a second partition of the target logical volume.

11. Apparatus for continuous data protection in a data storage system, the apparatus comprising:

a control unit, which is adapted to;

receive a first write command to write first data to a partition of a logical volume;

in response to the first write command, generate a first partition descriptor record (PDR) having a first timestamp;

store the first data at a first physical location;

associate the first PDR with the first physical location;

receive a second write command, subsequent to the first write command, to update the first data with second data;

responsively to the second write command, generate a second PDR having a second timestamp;

store the second data at a second physical location;

associate the second PDR with the second physical location;

generate a pointer between the first PDR and the second PDR; and

access the first PDR using the pointer in response to a read command indicating a time prior to the second timestamp.

12. The apparatus according to claim 11, wherein the control unit is adapted to associate the partition of the logical volume with the first PDR.

13. The apparatus according to claim 12, wherein the control unit is adapted to disassociate the partition from the first PDR and to associate the partition with the second PDR.

14. The apparatus according to claim 12, wherein the control unit is adapted to generate a pointer to the first PDR in a partition hash table.

15. The apparatus according to claim 11, wherein the control unit is adapted to link the first and second PDRs to each other by a binary tree responsively to one or more write commands subsequent to the first and the second write commands.

16. The apparatus according to claim 15, wherein the control unit is adapted to generate the binary tree by an Adelson-Velskii and Landis (AVL) method.

17. The apparatus according to claim 11, wherein the control unit is adapted to compare the first timestamp with the time indicated by the read command.

18. The apparatus according to claim 11, wherein the control unit is adapted to compare the first timestamp with the time indicated by the read command and with a predetermined threshold period of time.

19. The apparatus according to claim 11, wherein the first PDR comprises a bitmap field and wherein the control unit is adapted to use the bitmap field to determine that the first write command and the second write command do not comprise a single split write command.

20. The apparatus according to claim 11, wherein the logical volume comprises a source logical volume, wherein the partition comprises a first partition, and wherein the control unit, responsively to a volume copy command to copy the source logical volume to a target logical volume, is adapted to:

generate a third PDR having the first timestamp;

associate the third PDR with the first physical location; and

associate with the third PDR a second partition of the target logical volume.