Continuous backup using a mirror device

• US 20070156982A1
• Filed: 01/03/2006
• Published: 07/05/2007
• Est. Priority Date: 01/03/2006
• Status: Abandoned Application

• Current Assignee: EMC Corporation (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Meiri, David, Bjornsson, Magnus
• Application Number:
  US11/324,747
• Publication Number:
  US 20070156982A1
• Time in Patent Office: Days
• US Class Current: 711/162
• CPC Class Codes: G06F 11/1451 by selection of backup contents
• CPC Class Codes: G06F 11/2064 while ensuring consistency
• CPC Class Codes: G06F 11/2074 Asynchronous techniques
• CPC Class Codes: G06F 12/0815 Cache consistency protocols
• CPC Class Codes: G06F 2201/855 Details of asynchronous mirroring using a journal to transfer not-yet-mirrored changes

Abstract

Providing continuous backup of a storage device includes subdividing the storage device into subsections, providing a mirror device of the storage device that contains a copy of data that is on the storage device when the continuous backup is initiated, providing a time indicator that is modified periodically, and, in response to a request to write new data to a particular subsection of the storage device at a particular time, maintaining data being overwritten by the new data according to the particular subsection and according to a value of the indicator at the particular time, where, for a first write after the continuous backup is initiated, data from the mirror device is used to maintain data being overwritten. The subsections may be tracks. Maintaining the data being overwritten may include constructing a linked list of portions of data for each of the subsections. The portions of data may have variable sizes.

Claims

1. A method of providing continuous backup of a storage device, comprising:

subdividing the storage device into subsections;

providing a mirror device of the storage device that contains a copy of data that is on the storage device when the continuous backup is initiated;

providing a time indicator that is modified periodically; and

in response to a request to write new data to a particular subsection of the storage device at a particular time, maintaining data being overwritten by the new data according to the particular subsection and according to a value of the indicator at the particular time, wherein, for a first write after the continuous backup is initiated, data from the mirror device is used to maintain data being overwritten.

2. A method, according to claim 1, wherein the subsections are tracks.

3. A method, according to claim 1, wherein maintaining the data being overwritten includes constructing a linked list of portions of data for each of the subsections.

4. A method, according to claim 3, wherein the portions of data have variable sizes.

5. A method, according to claim 1, wherein in response to two data write operations to a particular subsection at a particular value of the indicator, data being written for each of the two data write operations is combined if data for the second data write operation is a subset of data for the first data write operation.

6. A method, according to claim 1, further comprising:

restoring the storage device to a state thereof at a particular point in time by writing the maintained data to the storage device.

7. A method, according to claim 6, wherein writing the maintained data to the storage device includes constructing subsections of the data by combining separate portions thereof corresponding to the same subsection.

8. A method, according to claim 1, further comprising:

inserting data for a particular subsection at a particular point in time by traversing data corresponding to the particular subsection to obtain an appropriate insertion point.

9. A method, according to claim 1, further comprising:

reading data for a particular subsection at a particular point in time by traversing data corresponding to the particular subsection and reading from the group consisting of;

data from the storage device, maintained data, and a combination of maintained data and data from the storage device.

10. A method, according to claim 1, further comprising:

compressing data by combining consecutive portions for a subsection.

11. Computer software, in a storage medium, that provides continuous backup of a storage device, comprising:

executable code that obtains a value of a time indicator that is modified periodically; and

executable code that, in response to a request to write new data to a particular subsection of the storage device at a particular time, maintains data being overwritten by the new data according to the particular subsection and according to a value of the indicator at the particular time wherein, for a first write after the continuous backup is initiated, data used to maintain data being overwritten is from a mirror device of the storage device, the mirror device containing a copy of data that is on the storage device when the continuous backup is initiated.

12. Computer software, according to claim 11, wherein the subsections are tracks.

13. Computer software, according to claim 11, wherein executable code that maintains the data being overwritten constructs a linked list of portions of data for each of the subsections.

14. Computer software, according to claim 13, wherein the portions of data have variable sizes.

15. Computer software, according to claim 11, wherein in response to two data write operations to a particular subsection at a particular value of the indicator, data being written for each of the two data write operations is combined if data for the second data write operation is a subset of data for the first data write operation.

16. Computer software, according to claim 11, further comprising:

executable code that restores the storage device to a state thereof at a particular point in time by writing the maintained data to the storage device.

17. Computer software, according to claim 16, wherein executable code that writes the maintained data to the storage device constructs subsections of the data by combining separate portions thereof corresponding to the same subsection.

18. Computer software, according to claim 11, further comprising:

executable code that inserts data for a particular subsection at a particular point in time by traversing data corresponding to the particular subsection to obtain an appropriate insertion point.

19. Computer software, according to claim 11, further comprising:

executable code that reads data for a particular subsection at a particular point in time by traversing data corresponding to the particular subsection and reading from the group consisting of;

data from the storage device, maintained data, and a combination of maintained data and data from the storage device.

20. Computer software, according to claim 11, further comprising:

executable code that compresses data by combining consecutive portions for a subsection.