Method and system for improving cache performance of a redundant disk array controller

1. A method comprising:

receiving a data transfer request pertaining to data;

determining whether the data transfer request is a read request or a write request;

when the data transfer request is the write request, writing the data to a non-volatile memory write cache;

when the data transfer request is the read request, determining whether the data are available from the volatile memory read cache;

when the data are available from the volatile memory read cache, obtaining the data from the volatile memory read cache and providing the data in response to the read request; when the data transfer request is the read request, determining whether the data are available from the non-volatile memory write cache; and when the data are available from the non-volatile memory write cache, obtaining the data from the non-volatile memory write cache and providing the data in response to the read request; and

when the data are not available from either the volatile memory read cache or the non-volatile memory write cache, obtaining the data from a redundant array of independent disks (RAID) virtual disk, storing the data in the volatile memory read cache, and providing the data in response to the read request.

2. The method of claim 1 further comprising:

when the data transfer request is the write request, writing the data to the non-volatile memory write cache and writing the data to the RAID virtual disk.

3. The method of claim 2 further comprising: when the data transfer request is the write request, copying the data to the volatile memory read cache.

4. The method of claim 1 further comprising:

detecting when a system power failure has occurred; and

when the system power failure has occurred, performing a flush of the volatile memory read cache to reset the volatile memory read cache to an empty state and restoring the non-volatile memory write cache to a previous write cache state as existed before the system power failure based on a retained state of non-volatile memory of the non-volatile write cache.

5. The method of claim 1 wherein the volatile memory read cache provides a volatile memory read cache capacity of two to six times a non-volatile memory write cache capacity of the non-volatile memory write cache.

6. The method of claim 1 wherein the volatile memory read cache provides a volatile memory read cache capacity of two to four times a non-volatile memory write cache capacity of the non-volatile memory write cache.

7. An information handling system comprising:

a redundant array of independent disks (RAID) storage subsystem, the RAID subsystem comprising:

a RAID virtual disk implemented using a plurality of RAID physical disks; and

a RAID controller, the RAID controller comprising:

a non-volatile memory write cache;

a volatile memory read cache; and

RAID control circuits, the RAID control circuits configured to:

receive a data transfer request pertaining to data;

determine whether the data transfer request is a read request or a write request;

when the data transfer request is the write request, write the data to the non-volatile memory write cache;

when the data transfer request is the read request, determine whether the data are available from the volatile memory read cache;

when the data are available from the volatile memory read cache, obtain the data from the volatile memory read cache and provide the data in response to the read request;

when the data transfer request is the read request, determine whether the data are available from the non-volatile memory write cache; and

when the data are available from the non-volatile memory write cache, obtain the data from the non-volatile memory write cache and provide the data in response to the read request; and

when the data are not available from either the volatile memory read cache or the non-volatile memory write cache, obtain the data from the RAID virtual disk, store the data in the volatile memory read cache, and provide the data in response to the read request.

8. The information handling system of claim 7 wherein the RAID control circuits are further configured, when the data transfer request is the write request, to write the data to the non-volatile memory write cache and to write the data to the RAID virtual disk.

9. The information handling system of claim 7 wherein the RAID control circuits are further configured, when the data transfer request is the write request, to copy the data to the volatile memory read cache.

10. The information handling system of claim 7 wherein the RAID control circuits are further configured to:

detect when a system power failure has occurred; and

when the system power failure has occurred, perform a flush of the volatile memory read cache to reset the volatile memory read cache to an empty state and restoring the non-volatile memory write cache to a previous write cache state as existed before the system power failure based on a retained state of non-volatile memory of the non-volatile write cache.

11. The information handling system of claim 7 wherein the volatile memory read cache provides a volatile memory read cache capacity of two to six times a non-volatile memory write cache capacity of the non-volatile memory write cache.

12. The information handling system of claim 7 wherein the volatile memory read cache provides a volatile memory read cache capacity of two to four times a non-volatile memory write cache capacity of the non-volatile memory write cache.

13. A redundant array of independent disks (RAID) controller comprising:

a non-volatile memory write cache;

a volatile memory read cache; and

RAID control circuits, the RAID control circuits configured to:

receive a data transfer request pertaining to data;

determine whether the data transfer request is a read request or a write request;

when the data transfer request is the write request, write the data to the non-volatile memory write cache;

when the data transfer request is the read request, determine whether the data are available from the volatile memory read cache;

when the data are available from the volatile memory read cache, obtain the data from the volatile memory read cache and provide the data in response to the read request; when the data transfer request is the read request, determining whether the data are available from the non-volatile memory write cache; and when the data are available from the non-volatile memory write cache, obtaining the data from the non-volatile memory write cache and providing the data in response to the read request; and

when the data are not available from either the volatile memory read cache or the non-volatile memory write cache, obtain the data from a RAID virtual disk coupled to the RAID controller, store the data in the volatile memory read cache, and provide the data in response to the read request.

14. The RAID controller of claim 13 wherein the RAID control circuits are further configured, when the data transfer request is the write request, to write the data to the non-volatile memory write cache and to write the data to the RAID virtual disk.

15. The RAID controller of claim 13 wherein the RAID control circuits are further configured, when the data transfer request is the write request, to copy the data to the volatile memory read cache.

16. The RAID controller of claim 13 wherein the volatile memory read cache provides a volatile memory read cache capacity of two to four times a non-volatile memory write cache capacity of the non-volatile memory write cache.

17. The RAID controller of claim 13 wherein the RAID control circuits are further configured to: detect when a system power failure has occurred, and when the system power failure has occurred, perform a flush of the volatile memory read cache to reset the volatile memory read cache to an empty state and restore the non-volatile memory write cache to a previous write cache state as existed before the system power failure based on a retained state of non-volatile memory of the non-volatile write cache.