HOST DISCOVERY AND HANDLING OF ALUA PREFERENCES AND STATE TRANSITIONS

• US 20120124312A1
• Filed: 11/12/2010
• Published: 05/17/2012
• Est. Priority Date: 11/12/2010
• Status: Active Grant

• Current Assignee: Veritas Technologies, LLC (Whitehouse Group Ltd.)
• Original Assignee: Symantec Corporation (NortonLifeLock Inc.)
• Inventors: Vemuri, Hari Krishna, Gosavi, Tushar Ravindranath, Gandhi, Neha Rajendraprasad
• Granted Patent: US 8,930,620 B2
• Time in Patent Office: Days
• US Class Current: 711/163
• CPC Class Codes: G06F 11/201 between storage system components
• CPC Class Codes: G06F 11/2092 Techniques of failing over between control units
• CPC Class Codes: G06F 3/0613 in relation to throughput
• CPC Class Codes: G06F 3/0635 by changing the path, e.g. traffic rerouting, path reconfiguration
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]

Abstract

Various systems and methods can discover asymmetric logical unit (LUN) access (ALUA) preferences and/or state transitions and use those preferences and/or state transitions to control how a host accesses a LUN in an ALUA array. One such method involves detecting a preferred controller for a LUN and then detecting that a current owner controller of the LUN is not the preferred controller. In response, the method can initiate an ownership change from the current owner controller to the preferred controller. Another method involves detecting an initial state of a first controller with respect to a LUN. The method then detects a subsequent state of the first controller with respect to the LUN subsequent to detecting the initial state. The method can then cause a computing device to access the LUN via a second controller, in response to the subsequent state not being the active optimized state.

Claims

1. A method comprising:

detecting a preferred controller for a logical unit (LUN) within an asymmetric LUN access (ALUA) array;

detecting that a current owner controller of the LUN is not the preferred controller; and

initiating an ownership change from the current owner controller to the preferred controller, wherein the detecting the preferred controller, the detecting the current owner controller, and the initiating are performed by a computing device implementing a multipathing agent.

2. The method of claim 1, wherein the detecting the preferred controller comprises accessing a static preference indicator provided by the ALUA array.

3. The method of claim 1, wherein the detecting the preferred controller comprises detecting status information associated with the current owner controller of the LUN.

4. The method of claim 1, wherein the detecting the preferred controller comprises receiving information identifying the preferred controller from an other node in a cluster, wherein the other node selected one of a plurality of controllers to be the preferred controller.

5. A method comprising:

detecting an initial state of a first controller in an ALUA array with respect to a LUN, wherein the initial state is an active optimized state;

detecting a subsequent state of the first controller with respect to the LUN, wherein the detecting the subsequent state is performed subsequent to the detecting the initial state, and wherein the detecting the subsequent state is not performed in response to receipt of a message indicating a state transition from the ALUA array; and

causing a computing device to access the LUN via a second controller, in response to the subsequent state not being the active optimized state, wherein the second controller is in the active optimized state when the causing is performed.

6. The method of claim 5, wherein the detecting the subsequent state comprises detecting an input/output performance decrease when the computing device accesses the LUN via the first controller.

7. The method of claim 5, wherein the detecting the subsequent state comprises requesting information identifying a state of the first controller with respect to the LUN from the ALUA array.

8. The method of claim 5, wherein the detecting the subsequent state is performed in response to the computing device receiving a request from an administrator.

9. The method of claim 5, wherein the detecting the subsequent state comprises detecting an input/output error when the computing device accesses the LUN via the first controller.

10. A computer readable storage medium comprising program instructions executable to:

detect a preferred controller for a logical unit (LUN) within an asymmetric LUN access (ALUA) array;

detect that a current owner controller of the LUN is not the preferred controller; and

initiate an ownership change from the current owner controller to the preferred controller.

11. The computer readable storage medium of claim 10, wherein detection of the preferred controller comprises accessing a static preference indicator provided by the ALUA array.

12. The computer readable storage medium of claim 10, wherein detection of the preferred controller comprises detecting status information associated with the current owner controller of the LUN.

13. A computer readable storage medium comprising program instructions executable to:

detect an initial state of a first controller in an ALUA array with respect to a LUN, wherein the initial state is an active optimized state;

detect a subsequent state of the first controller with respect to the LUN, wherein detection of the subsequent state is performed subsequent to detection of the initial state, and wherein detection of the subsequent state is not performed in response to receipt of a message indicating a state transition from the ALUA array; and

cause a computing device to access the LUN via a second controller, in response to the subsequent state not being the active optimized state, wherein the second controller is in the active optimized state when the computing device is caused to access the LUN via the second controller.

14. The computer readable storage medium of claim 13, wherein detection of the subsequent state comprises detection of an input/output performance decrease when the computing device accesses the LUN via the first controller.

15. The computer readable storage medium of claim 13, wherein detection of the subsequent state is performed by requesting information identifying a state of with the first controller with respect to the LUN from the ALUA array.

16. A system comprising:

one or more processors; and

memory coupled to the one or more processors, wherein the memory stores program instructions executable by the one or more processors to;

detect a preferred controller for a logical unit (LUN) within an asymmetric LUN access (ALUA) array;

detect that a current owner controller of the LUN is not the preferred controller; and

initiate an ownership change from the current owner controller to the preferred controller.

17. The system of claim 16, wherein detection of the preferred controller comprises accessing a static preference indicator provided by the ALUA array.

18. The system of claim 16, wherein detection of the preferred controller comprises detecting status information associated with the current owner controller of the LUN.

19. A system comprising:

one or more processors; and

memory coupled to the one or more processors, wherein the memory stores program instructions executable by the one or more processors to;

detect an initial state of a first controller in an ALUA array with respect to a LUN, wherein the initial state is an active optimized state;

detect a subsequent state of the first controller with respect to the LUN, wherein detection of the subsequent state is performed subsequent to detection of the initial state, and wherein detection of the subsequent state is not performed in response to receipt of a message indicating a state transition from the ALUA array; and

cause a computing device to access the LUN via a second controller, in response to the subsequent state not being the active optimized state, wherein the second controller is in the active optimized state when the computing device is caused to access the LUN via the second controller.

20. The system of claim 19, wherein detection of the subsequent state comprises detection of an input/output performance decrease when the computing device accesses the LUN via the first controller.

21. The system of claim 19, wherein detection of the subsequent state is performed by requesting information identifying a state of with the first controller with respect to the LUN from the ALUA array.