Redirection of storage access requests

• US 20060161700A1
• Filed: 01/14/2005
• Published: 07/20/2006
• Est. Priority Date: 01/14/2005
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Day, Kenneth Fairclough III, Boyd, Kenneth Wayne, Wolfgang, John Jay, Lickel, Charles William
• Granted Patent: US 7,366,846 B2
• Time in Patent Office: Days
• US Class Current: 710/61
• CPC Class Codes: G06F 11/2069 Management of state, configuration or failover
• CPC Class Codes: G06F 11/2076 Synchronous techniques

Abstract

Provided are a method, system, and article of manufacture, wherein a controller receives a request from one of a plurality of hosts. The controller determines whether a primary storage control unit coupled to the controller is operational. A response is generated by accessing the primary storage control unit, in response to determining that the primary storage control unit is operational. The response is generated by accessing a secondary storage control unit, in response to determining that the primary storage control unit is not operational, wherein data is replicated synchronously from the primary storage control unit to the secondary storage control unit.

Claims

1. A method, comprising:

receiving, at a controller, a request from one of a plurality of hosts;

determining, by the controller, whether a primary storage control unit coupled to the controller is operational;

generating a response by accessing the primary storage control unit, in response to determining that the primary storage control unit is operational; and

generating the response by accessing a secondary storage control unit, in response to determining that the primary storage control unit is not operational, wherein data is replicated synchronously from the primary storage control unit to the secondary storage control unit.

2. The method of claim 1, wherein the controller includes a cache, and wherein the method further comprises:

determining whether write caching is enabled in the controller; and

updating the secondary storage control unit with contents of the cache, prior to the generating of the response by accessing the secondary storage control unit.

3. The method of claim 1, wherein the controller includes a cache, wherein write caching is enabled in the controller, wherein the request is a write request, and wherein the method further comprises:

writing the data to the cache in response to receiving the write request; and

responding to the one of the plurality of hosts from which the write request was received that the write request has been executed, wherein the data written to the cache is destaged periodically to;

(i) the primary storage control unit, in response to determining that that primary storage control unit is operational; and

(ii) the secondary storage control unit, in response to determining that the primary storage control unit is not operational.

4. The method of claim 1, wherein the plurality of hosts operate without any notification that indicates to the plurality of hosts which storage control unit satisfies requests from the hosts.

5. The method of claim 1, wherein the controller includes a cache, wherein write caching is enabled, wherein the request is a read request, and wherein the method further comprises:

satisfying the read request from the cache, in response to determining that the read request can be satisfied from the cache;

satisfying the read request from the primary storage control unit if the primary storage control unit is operational, in response to determining that the read request cannot be satisfied from the cache;

updating the secondary storage control unit with contents of the cache if the primary storage control unit is not operational; and

satisfying the read request from the secondary storage control unit subsequent to the updating of the secondary storage control unit.

6. The method of claim 1, wherein the data is synchronously replicated between the primary storage control unit and the secondary storage control unit by:

sending, by the primary storage control unit, a completion notification to the controller after an update to the primary storage control unit has been copied to the secondary storage control unit, wherein the primary storage control unit and the secondary storage control unit include identical data after the data is replicated synchronously.

7. The method of claim 1, wherein a plurality of operating systems are executing on the plurality of hosts, and wherein a single application in the controller enables the plurality of hosts to access data stored in the primary storage control unit and the secondary storage control unit, and wherein if the primary storage control unit is operational then the primary storage control unit is available for processing data transfer requests generated by the plurality of hosts.

8. The method of claim 1, wherein the controller is a storage area network volume controller that controls storage volumes in the primary and the secondary storage control units, wherein the primary storage control unit is a primary storage controller, wherein the secondary storage control unit is a secondary storage controller, wherein a redirection application on the storage area network volume controller performs the receiving, the determining, the generating of the response by accessing the primary storage controller, and the generating of the response by accessing the secondary storage controller.

9. A system, comprising:

memory; and

processor coupled to the memory, wherein the processor is capable of performing operations, the operations comprising;

(i) receiving a request from one of a plurality of hosts;

(ii) determining whether a primary storage control unit is operational;

(iii) generating a response by accessing the primary storage control unit, in response to determining that the primary storage control unit is operational; and

(iv) generating the response by accessing a secondary storage control unit, in response to determining that the primary storage control unit is not operational, wherein data is replicated synchronously from the primary storage control unit to the secondary storage control unit.

10. The system of claim 9, further comprising:

a cache, and wherein the operations further comprise;

(i) determining whether write caching is enabled; and

(ii) updating the secondary storage control unit with contents of the cache, prior to the generating of the response by accessing the secondary storage control unit.

11. The system of claim 9, further comprising:

a cache, wherein write caching is enabled, wherein the request is a write request, and wherein the operations further comprise;

(a) writing the data to the cache in response to receiving the write request; and

(b) responding to the one of the plurality of hosts from which the write request was received that the write request has been executed, wherein the data written to the cache is destaged periodically to;

(i) the primary storage control unit, in response to determining that that primary storage control unit is operational; and

(ii) the secondary storage control unit, in response to determining that the primary storage control unit is not operational.

12. The system of claim 9, wherein the plurality of hosts operate without any notification that indicates to the plurality of hosts which storage control unit satisfies requests from the hosts.

13. The system of claim 9, further comprising:

a cache, wherein write caching is enabled, wherein the request is a read request, and wherein the operations further comprise;

(a) satisfying the read request from the cache, in response to determining that the read request can be satisfied from the cache;

(b) satisfying the read request from the primary storage control unit if the primary storage control unit is operational, in response to determining that the read request cannot be satisfied from the cache;

(c) updating the secondary storage control unit with contents of the cache if the primary storage control unit is not operational; and

(d) satisfying the read request from the secondary storage control unit subsequent to the updating of the secondary storage control unit.

14. The system of claim 9, wherein the data is synchronously replicated between the primary storage control unit and the secondary storage control unit by:

sending, by the primary storage control unit, a completion notification after an update to the primary storage control unit has been copied to the secondary storage control unit, wherein the primary storage control unit and the secondary storage control unit include identical data after the data is replicated synchronously.

15. The system of claim 9, wherein a plurality of operating systems are executing on the plurality of hosts, and wherein a single application enables the plurality of hosts to access data stored in the primary storage control unit and the secondary storage control unit, and wherein if the primary storage control unit is operational then the primary storage control unit is available for processing data transfer requests generated by the plurality of hosts.

16. The system of claim 9, wherein the system is a storage area network volume controller that controls storage volumes in the primary and the secondary storage control units, wherein the primary storage control unit is a primary storage controller, wherein the secondary storage control unit is a secondary storage controller, wherein a redirection application on the storage area network volume controller performs the receiving, the determining, the generating of the response by accessing the primary storage controller, and the generating of the response by accessing the secondary storage controller.

17. An article of manufacture, wherein the article of manufacture is capable of causing operations, the operations comprising:

receiving, at a controller, a request from one of a plurality of hosts;

determining, by the controller, whether a primary storage control unit coupled to the controller is operational;

generating a response by accessing the primary storage control unit, in response to determining that the primary storage control unit is operational; and

generating the response by accessing a secondary storage control unit, in response to determining that the primary storage control unit is not operational, wherein data is replicated synchronously from the primary storage control unit to the secondary storage control unit.

18. The article of manufacture of claim 17, wherein the controller includes a cache, and wherein the operations further comprise:

determining whether write caching is enabled in the controller; and

updating the secondary storage control unit with contents of the cache, prior to the generating of the response by accessing the secondary storage control unit.

19. The article of manufacture of claim 17, wherein the controller includes a cache, wherein write caching is enabled in the controller, wherein the request is a write request, and wherein the operations further comprise:

writing the data to the cache in response to receiving the write request; and

responding to the one of the plurality of hosts from which the write request was received that the write request has been executed, wherein the data written to the cache is destaged periodically to;

(i) the primary storage control unit, in response to determining that that primary storage control unit is operational; and

(ii) the secondary storage control unit, in response to determining that the primary storage control unit is not operational.

20. The article of manufacture of claim 17, wherein the plurality of hosts operate without any notification that indicates to the plurality of hosts which storage control unit satisfies requests from the hosts.

21. The article of manufacture of claim 17, wherein the controller includes a cache, wherein write caching is enabled, wherein the request is a read request, and wherein the operations further comprise:

satisfying the read request from the cache, in response to determining that the read request can be satisfied from the cache;

satisfying the read request from the primary storage control unit if the primary storage control unit is operational, in response to determining that the read request cannot be satisfied from the cache;

updating the secondary storage control unit with contents of the cache if the primary storage control unit is not operational; and

satisfying the read request from the secondary storage control unit subsequent to the updating of the secondary storage control unit.

22. The article of manufacture of claim 17, wherein the data is synchronously replicated between the primary storage control unit and the secondary storage control unit by:

sending, by the primary storage control unit, a completion notification to the controller after an update to the primary storage control unit has been copied to the secondary storage control unit, wherein the primary storage control unit and the secondary storage control unit include identical data after the data is replicated synchronously.

23. The article of manufacture of claim 17, wherein a plurality of operating systems are executing on the plurality of hosts, and wherein a single application in the controller enables the plurality of hosts to access data stored in the primary storage control unit and the secondary storage control unit, and wherein if the primary storage control unit is operational then the primary storage control unit is available for processing data transfer requests generated by the plurality of hosts.

24. The article of manufacture of claim 17, wherein the controller is a storage area network volume controller that controls storage volumes in the primary and the secondary storage control units, wherein the primary storage control unit is a primary storage controller, wherein the secondary storage control unit is a secondary storage controller, wherein a redirection application on the storage area network volume controller performs the receiving, the determining, the generating of the response by accessing the primary storage controller, and the generating of the response by accessing the secondary storage controller.

25. A method for deploying computing infrastructure, comprising integrating computer-readable code into a computing system, wherein the code in combination with the computing system is capable of performing:

receiving, at a controller, a request from one of a plurality of hosts;

determining, by the controller, whether a primary storage control unit coupled to the controller is operational;

generating a response by accessing the primary storage control unit, in response to determining that the primary storage control unit is operational; and

generating the response by accessing a secondary storage control unit, in response to determining that the primary storage control unit is not operational, wherein data is replicated synchronously from the primary storage control unit to the secondary storage control unit.

26. The method of claim 25, wherein the controller includes a cache, and wherein the, wherein the code in combination with the computing system is further capable of performing:

determining whether write caching is enabled in the controller; and

updating the secondary storage control unit with contents of the cache, prior to the generating of the response by accessing the secondary storage control unit.

27. The method of claim 25, wherein the controller includes a cache, wherein write caching is enabled in the controller, wherein the request is a write request, and wherein the code in combination with the computing system is further capable of performing:

writing the data to the cache in response to receiving the write request; and

responding to the one of the plurality of hosts from which the write request was received that the write request has been executed, wherein the data written to the cache is destaged periodically to;

(i) the primary storage control unit, in response to determining that that primary storage control unit is operational; and

(ii) the secondary storage control unit, in response to determining that the primary storage control unit is not operational.

28. The method of claim 25, wherein the controller includes a cache, wherein write caching is enabled, wherein the request is a read request, wherein the code in combination with the computing system is further capable of performing:

satisfying the read request from the cache, in response to determining that the read request can be satisfied from the cache;

satisfying the read request from the primary storage control unit if the primary storage control unit is operational, in response to determining that the read request cannot be satisfied from the cache;

updating the secondary storage control unit with contents of the cache if the primary storage control unit is not operational; and

satisfying the read request from the secondary storage control unit subsequent to the updating of the secondary storage control unit.

29. The method of claim 25, wherein the data is synchronously replicated between the primary storage control unit and the secondary storage control unit by:

sending, by the primary storage control unit, a completion notification to the controller after an update to the primary storage control unit has been copied to the secondary storage control unit, wherein the primary storage control unit and the secondary storage control unit include identical data after the data is replicated synchronously.

30. The method of claim 25, wherein the controller is a storage area network volume controller that controls storage volumes in the primary and the secondary storage control units, wherein the primary storage control unit is a primary storage controller, wherein the secondary storage control unit is a secondary storage controller, wherein a redirection application on the storage area network volume controller performs the receiving, the determining, the generating of the response by accessing the primary storage controller, and the generating of the response by accessing the secondary storage controller.