Method and system for storing data using a continuous data protection system

• US 7,797,582 B1
• Filed: 08/03/2007
• Issued: 09/14/2010
• Est. Priority Date: 02/04/2004
• Status: Active Grant

• Current Assignee: NetApp, Inc.
• Original Assignee: NetApp, Inc.
• Inventors: Trimmer, Don Alvin, Johnson, Randall, Chang, Yafen Peggy, Johnston, Craig Anthony, Stager, Roger Keith, Saxena, Pawan, Blaser, Rico
• Primary Examiner(s): LE, DIEU MINH T
• Application Number:
  US11/833,515
• Time in Patent Office: 1,138 Days
• Field of Search: 714/2, 714 5- 8, 714 11- 13, 714/15, 714/42, 714/52, 707/200, 707/202, 707/204
• US Class Current: 714/42
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: G06F 11/2074 Asynchronous techniques

Abstract

A method for tracking changes on a primary volume in a continuous data protection system writes data to the primary volume. A copy of the data is written to a secondary volume, the secondary volume including all writes made to the primary volume. Each write made to the secondary volume is mapped in a data structure, such that the data structure tracks changes on the primary volume between two different points in time.

Claims

1. A method comprising:

writing data from a host computer to a primary volume;

writing a copy of the data, from the host computer via a data protection system, to a secondary volume in consecutive physical locations, so that the secondary volume includes the data written to the primary volume; and

mapping each write made to the secondary volume in a data structure which tracks changes on the primary volume between two different points in time.

2. The method according to claim 1, wherein the data structure corresponds to a particular time period and includes a list of all blocks on the primary volume that have changed between the two different points in time.

3. The method according to claim 2, wherein the data structure is used to locate a recovery point for the primary volume, the recovery point corresponding to a time period covered by the data structure.

4. The method according to claim 1, wherein the data structure includes a block-based list of the data written to the primary volume.

5. The method according to claim 4, wherein the data structure includes a region of the primary volume where a write is made, a block offset within the region of the primary volume where the write is made, and a location on the secondary volume where the write begins.

6. The method according to claim 1, wherein multiple data structures are used, each data structure corresponding to a particular time period and including all writes made to the primary volume during the time period, the multiple data structures permitting a larger time period to be protected than a single data structure.

7. The method according to claim 6, wherein the multiple data structures are merged into a single merged data structure, so that the multiple time periods protected by the multiple data structures are protected by the single merged data structure.

8. The method according to claim 1, wherein the data structure can be used to selectively play back a portion of the writes made to the primary volume during the two points in time that correspond to the data structure.

9. A computer-readable storage medium storing a set of instructions for execution by a general purpose computer to track changes on a primary volume, the set of instructions comprising:

a first writing code segment for writing data from a host computer to the primary volume;

a second writing code segment for writing a copy of the data, from the host computer via a data protection system, to a secondary volume in consecutive physical locations, so that the secondary volume includes the data written to the primary volume; and

a mapping code segment for mapping each write made to the secondary volume in a data structure which tracks changes on the primary volume between two different points in time.

10. The computer-readable storage medium according to claim 9, wherein multiple data structures are used, each data structure corresponding to a particular time period and including all writes made to the primary volume during the time period, the multiple data structures permitting a larger time period to be protected than a single data structure, the set of instructions further comprising:

a merging code segment for merging multiple data structures into a single merged data structure, whereby the multiple time periods protected by the multiple data structures are protected by the single merged data structure.

11. A system comprising:

a data protection system coupled to a host computer for protecting data written from the host computer, wherein the data includes a plurality of blocks;

a primary volume configured to write the data from the host computer;

a secondary volume configured to write a copy of the data from the host computer, via the data protection system, so that the plurality of blocks are in consecutive physical locations, wherein the data protection system is configured to map writes made to the secondary volume in a data structure which tracks changes made on the primary volume between two different points in time.

12. The system according to claim 11, wherein the data structure corresponds to a particular time period and includes a list of all blocks on the primary volume that have changed between the two different points in time.

13. The system according to claim 11, wherein the data structure is used to locate a recovery point for the primary volume, the recovery point corresponding to a time period covered by the data structure.

14. The system according to claim 11, wherein the data structure includes a block-based list of the data written to the primary volume.

15. The system according to claim 14, wherein the data structure includes a region of the primary volume where a write is made, a block offset within the region of the primary volume where the write is made, and a location on the secondary volume where the write begins.

16. The system according to claim 11, wherein multiple data structures are used, each data structure corresponding to a particular time period and including all writes made to the primary volume during the time period, the multiple data structures permitting a larger time period to be protected than a single data structure.

17. The system according to claim 16, wherein the multiple data structures can be merged into a single merged data structure, so that the multiple time periods protected by the multiple data structures are protected by the single merged data structure.

18. The system according to claim 11, wherein the data structure can be used to selectively play back a portion of the writes made to the primary volume during the two points in time that correspond to the data structure.