Methods and systems using solid-state drives as storage controller cache memory

• US 8,938,574 B2
• Filed: 10/25/2011
• Issued: 01/20/2015
• Est. Priority Date: 10/26/2010
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: LSI Corporation (Broadcom, Inc.)
• Inventors: Smith, Gerald E., Hallyal, Basavaraj G.
• Primary Examiner(s): CARDWELL, ERIC
• Application Number:
  US13/281,301
• Publication Number:
  US 20120102268A1
• Time in Patent Office: 1,183 Days
• Field of Search: None
• US Class Current: 711/103
• CPC Class Codes: G06F 11/2071 using a plurality of controllers
• CPC Class Codes: G06F 11/2089 Redundant storage control functionality
• CPC Class Codes: G06F 12/084 with a shared cache
• CPC Class Codes: G06F 12/0873 Mapping of cache memory to specific storage devices or parts thereof
• CPC Class Codes: G06F 2212/1016 Performance improvement
• CPC Class Codes: G06F 2212/222 Non-volatile memory

Abstract

Methods and systems for using one or more solid-state drives (SSDs) as a shared cache memory for a plurality of storage controllers coupled with the SSDs and coupled with a plurality of storage devices through a common switched fabric communication medium. All controllers share access to the SSDs through the switched fabric and thus can assume control for a failed controller by, in part, accessing cached data of the failed controller in the shared SSDs.

Claims

1. A system comprising:

a plurality of storage controllers adapted to couple with one or more host systems;

a plurality of storage devices for persistent storage of user data received from the one or more host systems;

a switched fabric communication medium coupling the plurality of storage controllers with each of the plurality of storage devices; and

a solid-state drive (SSD);

wherein each of the plurality of storage controllers is coupled through the switched fabric communication medium with the SSD, each of the plurality of storage controllers uses a different portion of the SSD as a cache memory, and

each of the plurality of storage controllers is operable to assume control for a failed storage controller by accessing, via the switched fabric communication medium, cached data for the failed storage controller in a portion of the SSD used by the failed storage controller.

2. The system of claim 1

wherein each of the plurality of storage controllers uses its portion of the SSD as a cache memory for a logical volume managed by the storage controller.

3. The system of claim 1

wherein each of the plurality of storage controllers uses the SSD as a cache memory by storing data for write requests from a host on the SSD.

4. The system of claim 1

wherein the system dynamically adjusts the size of the portion corresponding to each storage controller based on a load associated with each storage controller.

5. The system of claim 1

wherein a plurality of logical volumes are configured on the plurality of storage devices by the plurality of storage controllers,

wherein each of the plurality of logical volumes is associated with a corresponding portion of the SSD, and

wherein each storage controller of the plurality of storage controllers uses as its cache memory a portion of the SSD corresponding to a logical volume accessed by a request from said each storage controller.

6. The system of claim 5

wherein the system dynamically adjusts the size of the portion of the SSD corresponding to each logical volume based on a load associated with each logical volume.

7. The system of claim 1

wherein each of the plurality of storage controllers is operable in a corresponding controller power domain of a plurality of controller power domains,

wherein the SSD, the plurality of storage devices, and the switched fabric communication medium are operable in one or more power domains separate from the plurality of controller power domains, and

whereby, responsive to loss of a controller power domain associated with a first storage controller, the SSD, the plurality of storage devices, and the switched fabric communication medium remain accessible to other storage controllers in other controller power domains through the switched fabric communication medium.

8. A system comprising:

a plurality of storage controllers adapted to couple with one or more host systems;

a plurality of storage devices for persistent storage of user data received from the one or more host systems;

a switched fabric communication medium coupling the plurality of storage controllers with each of the plurality of storage devices, the switched fabric communication medium comprising two switching devices,

wherein each switching device comprises a solid-state drive (SSD), and each SSD is used to cache data received from the plurality of storage controllers in processing write requests from attached host systems directed to one or more of the plurality of storage devices, and

wherein each of the two switching devices mirrors cached data from its SSD to the SSD of the other of the two switching devices using the switched fabric communication medium,

wherein each of the plurality of storage controllers uses a different portion of the SSDs as a cache memory, and each of the plurality of storage controllers is operable to assume control for a failed storage controller by accessing, via the switched fabric communication medium, cached data for the failed storage controller in a portion of the SSDs used by the failed storage controller.

9. The system of claim 8

wherein the switching devices associate each of the plurality of storage controllers with a corresponding portion for a logical volume managed by the storage controller.

10. The system of claim 8

wherein each of the switching devices comprises a Serial Attached Small Computer System Interface (SAS) expander.

11. The system of claim 8

wherein each switching device dynamically adjusts the size of the portion corresponding to each storage controller based on a load associated with each storage controller.

12. The system of claim 8

wherein a plurality of logical volumes are configured on the plurality of storage devices by the plurality of storage controllers,

wherein each of the plurality of logical volumes is associated with a corresponding portion of the SSD of each switching device, and

wherein each storage controller of the plurality of storage controllers uses as its cache memory a portion of the SSD of each switching device corresponding to a logical volume accessed by a request from said each storage controller.

13. The system of claim 12

wherein each switching device dynamically adjusts the size of the portion of its SSD corresponding to each logical volume based on a load associated with each logical volume.

14. The system of claim 8, further comprising:

a plurality of power domains wherein each of the plurality of storage controllers is operable in a corresponding controller power domain of the plurality of controller power domains; and

one or more storage power domains separate from the plurality of controller power domains, wherein the plurality of storage devices and the switched fabric communication medium are operable in the one or more storage power domains, and

whereby, responsive to loss of a controller power domain associated with a first storage controller, the switched fabric communication medium and the plurality of storage devices remain accessible to other storage controllers in other controller power domains through the switched fabric communication medium.

15. A method operable in a system, the system comprising a plurality of storage controllers coupled with a plurality of storage devices through a switched fabric communication medium, the system further comprising a solid-state drive (SSD), wherein each of the plurality of storage controllers is coupled through the switched fabric communication medium to the SSD, and each of the plurality of storage controllers uses a different portion of the SSD as a cache memory, the method comprising:

receiving a write request in a storage controller of the plurality of storage controllers, the write request directed to a logical volume configured on portions of one or more of the plurality of storage devices;

caching data associated with the write request from the storage controller into the SSD;

receiving another write request in another storage controller of the plurality of storage controllers, the write request directed to a logical volume configured on portions of one or more of the plurality of storage devices;

caching data associated with the other write request from the other storage controller into the SSD;

flushing cached data from the SSD for persistent storage; and

assuming control for a failed storage controller by accessing, via the switched fabric communication medium, cached data for the failed storage controller in a portion of the SSD used by the failed storage controller.

16. The method of claim 15 further comprising:

allocating a corresponding portion of the SSD for use by each controller of the plurality of storage controllers to cache data associated with a received write request for a logical volume managed by the storage controller.

17. The method of claim 15 further comprising:

adjusting a size of a portion of the SSD corresponding to a storage controller based on a load associated with the storage controller.

18. The method of claim 15

wherein a plurality of logical volumes are configured on corresponding portions of one or more of the plurality of storage devices,

wherein the method further comprises:

allocating a corresponding portion of the SSD for each of the plurality of logical volumes wherein each storage controller uses the corresponding portion for a logical volume accessed by said each storage controller in processing a received write request to cache data associated with the write request.

19. A method operable in a system, the system comprising a plurality of storage controllers coupled with a plurality of storage devices through a switched fabric communication medium, the switched fabric communication medium comprising two switching devices coupling each of the plurality of storage controllers with each of the plurality of storage devices, each switching device comprising a solid-state drive (SSD), wherein each of the plurality of storage controllers is coupled through the switched fabric communication medium with each of the SSDs, and each of the plurality of storage controllers uses a different portion of the SSD as a cache memory, the method comprising:

receiving a write request in a storage controller of the plurality of storage controllers, the write request directed to a logical volume configured on portions of one or more of the plurality of storage devices;

caching data associated with the write request from the storage controller into the SSD of one or more of the switching devices;

synchronizing cached data between the two switching devices;

flushing cached data from the SSD of one or more of the switching devices to the logical volume for persistent storage;

receiving another write request in another storage controller of the plurality of storage controllers, the other write request directed to a logical volume configured on portions of one or more of the plurality of storage devices;

caching data associated with the other write request from the other storage controller into the SSD of one or more of the switching devices; and

assuming control for a failed storage controller by accessing, via the switched fabric communication medium, cached data for the failed storage controller in a portion of the SSDs used by the failed storage controller.

20. The method of claim 19

wherein each of the switching devices comprises a Serial Attached Small Computer System Interface (SAS) expander.