PERFORMING MIRRORING OF A LOGICAL STORAGE UNIT

• US 20100306488A1
• Filed: 01/03/2008
• Published: 12/02/2010
• Est. Priority Date: 01/03/2008
• Status: Active Grant

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Inventors: Stroberger, Christopher
• Granted Patent: US 9,471,449 B2
• Time in Patent Office: Days
• US Class Current: 711/162
• CPC Class Codes: G06F 11/2064 while ensuring consistency
• CPC Class Codes: G06F 11/2074 Asynchronous techniques
• CPC Class Codes: G06F 3/0614 Improving the reliability of storage systems
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/0683 Plurality of storage devices

Abstract

Mirroring of a logical storage unit initially associated with a first controller is performed, where the first log segment associated with the first controller is maintained of writes by the first controller to the logical storage unit. The first log segment is for use in mirroring writes to a mirror system. Control of the logical storage unit is transferred from the first controller to at least a second controller, and in response to the transfer, a first marker is provided in the first log segment to enable the mirror system to synchronize mirrored writes corresponding to writes to the logical storage units by the first controller and at least a second controller.

Claims

1. A method comprising:

performing mirroring of a logical storage unit initially associated with a first controller, wherein a first log segment associated with the first controller is maintained of writes by the first controller to the logical storage unit, the first log segment for use in mirroring writes to a mirror system;

transferring control of the logical storage unit from the first controller to at least a second controller; and

in response to the transfer, providing a first marker in the first log segment to enable the mirror system to synchronize mirrored writes corresponding to writes to the logical storage unit by the first controller and at least the second controller.

2. The method of claim 1, further comprising:

after the transfer, maintaining a second log segment associated with at least the second controller of writes by at least the second controller to the logical storage unit; and

performing mirroring of the writes by at least the second controller to the mirror system according to the second log segment.

3. The method of claim 2, further comprising:

providing a second marker in the second log segment, wherein the second marker in conjunction with the first marker enables the mirror system to synchronize mirrored writes corresponding to writes to the logical storage unit by the first controller and at least the second controller.

4. The method of claim 3, wherein providing the first marker and the second marker comprises providing the first and second markers having the same value.

5. The method of claim 4, wherein providing the first and second markers comprises providing a unique serial number.

6. The method of claim 3, wherein providing the first marker comprises providing the first marker as a last entry in the first log segment, and wherein providing the second marker comprises providing the second marker as a first entry of the second log segment.

7. The method of claim 6, further comprising:

in response to detecting receipt of the second marker, the mirror system holding off mirroring writes by the second controller to the logical storage unit.

8. The method of claim 7, further comprising:

the mirror system enabling mirroring of the writes by the second controller to the logical storage unit in response to detecting receipt of the first marker.

9. The method of claim 2, further comprising:

transferring control of the logical storage unit from the second controller to one of the first controller and a third controller;

in response to transferring control of the logical storage unit from the second controller, providing a third marker in the second log segment, and creating a third log segment associated with the first or third controller that also contains the third marker.

10. The method of claim 9, further comprising:

performing additional transfers of the logical storage unit among a cluster of storage controllers including at least the first, second, and third controllers; and

adding additional markers in response to the additional transfers, the additional markers to the corresponding log segments to enable the mirror system to perform mirrored writes corresponding to the writes by the storage controllers of the cluster in an original order of the writes by the storage controllers of the cluster.

11. The method of claim 1, wherein performing the mirroring of the logical storage unit comprises performing asynchronous mirroring of the logical storage unit at the mirror system.

12. The method of claim 1, wherein performing the mirroring of the logical storage unit comprises performing synchronous mirroring of the logical storage unit at the mirror system, the method further comprising:

converting the synchronous mirroring to asynchronous mirroring as part of a procedure for transferring the logical storage unit from the first controller to at least the second controller.

13. The method of claim 1, wherein performing the mirroring of the logical storage unit comprises the first controller sending content of the first log segment to the mirror system.

14. An article comprising at least one computer-readable storage medium containing instructions that when executed cause a first storage controller to:

receive write requests to perform writes to a logical storage unit;

in response to the write requests, creating a first log segment containing entries for the write requests;

transmit information from the entries of the first log segment to a mirror system to replicate the writes to a mirror copy of the logical storage unit;

receive at least one command to transfer control of the logical storage unit from the first storage controller to a second, different storage controller;

in response to the at least one command to transfer control of the logical storage unit, add a marker to the first log segment; and

transmit the marker from the first log segment to the mirror system to allow the mirror system to synchronize replication of writes to the mirror copy of the logical storage unit performed by multiple storage controllers.

15. The article of claim 14, wherein the instructions when executed cause the first storage controller to further:

send the marker to the second storage controller to allow the second storage controller to store the marker in a second log segment corresponding to the logical storage unit.

16. The article of claim 15, wherein the instructions when executed cause the first storage controller to further:

exchange messaging with the second storage controller to transfer control of the logical storage unit to the second storage controller; and

terminate the first log segment.

17. The article of claim 16, wherein the instructions when executed cause the first storage controller to further:

exchange messaging with the second storage controller to cause control of logical storage unit to be transferred back from the second storage controller to the first storage controller; and

in response to the exchange of messaging to transfer control of the logical storage unit back to the first storage controller, create another log segment containing entries corresponding to writes to the logical storage unit performed by the first storage controller; and

add a second marker to the other log segment; and

transmit the second marker to the mirror system to allow the mirror system to hold off replication of writes indicated by the another log segment until after all writes associated with the second storage controller have been replicated by the mirror system.

18. A storage subsystem comprising:

a cluster of storage controllers; and

a pool of storage resources accessible by the storage controllers, wherein at least one logical storage unit is defined on the pool of storage resources,

the storage controllers to maintain corresponding log segments containing entries for writes performed to the logical storage unit performed by respective storage controllers,

wherein at least some of the log segments contain markers to be communicated by corresponding storage controllers to a remote mirror system to enable the remote mirror system to replicate writes corresponding to the at least some log segments in original order of the writes.

19. The storage subsystem of claim 18, wherein the storage controllers comprise a first storage controller and a second storage controller, wherein the first storage controller receives a command to transfer control of the logical storage unit to the second storage controller, and in response to such command, the first storage controller to add a first marker as an entry in the log segment associated with the first storage controller.

20. The storage subsystem of claim 19, wherein the first storage controller communicates the first marker to the second storage controller, the second storage controller to add the first marker to the log segment associated with the second storage controller.