System and method for servicing requests to a storage array

• US 20030005354A1
• Filed: 06/28/2001
• Published: 01/02/2003
• Est. Priority Date: 06/28/2001
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Kalman, Dean Alan
• Granted Patent: US 6,820,211 B2
• Time in Patent Office: Days
• US Class Current: 714/7
• CPC Class Codes: G06F 11/1088 Reconstruction on already foreseen single or plurality of spare disks
• CPC Class Codes: G06F 11/1405 at machine instruction level
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: G06F 2211/1054 Parity-fast hardware, i.e. dedicated fast hardware for RAID systems with parity

Abstract

According to the method of the present invention, if a data read request to an unavailable particular storage medium is received from a system processor, a request servicing circuit of an adapter reconstructs the request data from data and parity data stored on other storage media in the array. However, if a data write request to an unavailable storage medium is received from the system processor, the actual data related to the data write request is stored in a temporary memory location, and the data write request is logged in a non-volatile memory. There is no built-in data redundancy in a first preferred embodiment of the present invention; thus, modified data is lost in the event of the failure of another storage medium during the update of the selected storage medium. However, a second preferred embodiment of the present invention incorporates a spare storage medium that preserves the modified data if another storage medium fails.

Claims

1. A method of servicing a request to a redundant storage array including a plurality of storage media containing data and related parity data, said method comprising:

receiving a data request for data stored by a selected storage medium among said plurality of storage media; and

in response to receiving said data request while an update to said selected storage medium is being performed, servicing said data request by reference to said data and said related parity data of other storage media among said plurality of storage media.

2. The method according to claim 1, said step of servicing further including:

automatically reconstructing requested data utilizing said data and related parity data from said other storage media; and

outputting said reconstructed requested data.

3. The method according to claim 2, said step of automatically reconstructing further including:

determining a type of said data request; and

automatically reconstructing requested data utilizing said data and said related parity data only in response to determining that said data request is a data read request.

4. The method according to claim 3, said step of determining further comprising:

in response to determining that said data request is a data write request, logging said data write request;

storing new data for said data write request;

setting said particular storage medium to a rebuild status;

rebuilding said particular storage medium utilizing said data and related parity data from said other storage media; and

setting said particular storage medium to online status.

5. The method according to claim 1, wherein said particular storage medium is a disk, and said redundant storage array is a redundant disk array and wherein:

receiving a data request for data stored by a particular storage medium comprises receiving a data request for data stored by a particular disk of said redundant disk array.

6. An adapter for use with a data processing system including a redundant storage array including a plurality of storage media containing data and related parity data, said adapter comprising:

an updating circuit for receiving a data request for data stored by a selected storage medium among said plurality of storage media; and

a request servicing circuit, in response to receiving said data request while an update to said selected storage medium is being performed, for servicing said data request by reference to said data and said related parity data of other storage media among said plurality of storage media.

7. The adapter according to claim 6, wherein said updating circuit is an adapter a processor.

8. The adapter according to claim 6, wherein said request servicing circuit is an exclusive-OR (XOR) processor for automatically reconstructing requested data utilizing data and related parity data from other storage media during said updating, in response to a data request by said system processor, said XOR processor coupled to an adapter processor.

9. The adapter according to claim 6, further including:

a non-volatile random access memory (NVRAM) for logging data write requests.

10. The adapter according to claim 6, further comprising:

a storage location for temporarily storing write data for said selected storage media during said updating.

11. The adapter according to claim 10, wherein said storage location is an adapter cache.

12. The adapter according to claim 11, wherein said adapter cache further includes:

a battery-backup circuit, for preserving data stored on said adapter cache.

13. The adapter according the claim 8, wherein said data request is a data read request.

14. A disk system comprising:

an adapter according to claim 6; and

a redundant storage array.

15. The adapter according to claim 6, wherein said redundant storage array is a redundant array of inexpensive disks (RAID).

17. The data processing system according to claim 16, wherein said redundant storage array is a redundant array of inexpensive disks (RAID).

18. The data processing system according to claim 16, wherein said redundant storage array stores data in stripes, wherein each said stripe further includes data and related parity data.

19. The data processing system according to claim 16, wherein said updating circuit is an adapter processor.

20. The data processing system according to claim 18, wherein said request servicing circuit is an exclusive-OR (XOR) processor for automatically reconstructing requested data utilizing said data said related parity data from other storage media during said updating, in response to a data request by said system processor, said XOR processor coupled to said adapter processor.

21. The data processing system according to claim 16, wherein said adapter further comprising:

a non-volatile random access memory (NVRAM) for logging all data write requests and data read-with-intent-to-write requests.

22. The data processing system according to claim 16, further including:

a storage location for temporarily storing all write data for said selected storage media during said updating.

23. The data processing system according to claim 22, wherein said storage location is a temporary space on other storage media of said redundant storage array.

24. The data processing system according to claim 22, wherein said storage location is an adapter cache.

25. The data processing system according to claim 24, wherein said adapter further includes a battery backup circuit.

16. A data processing system, comprising:

a system processor;

a system memory coupled to said system processor;

a redundant storage array; and

an adapter including a redundant storage array including a plurality of storage media containing data and related parity data, said adapter further including;

an updating circuit for receiving a data request for data stored by a selected storage medium among said plurality of storage media; and

a request servicing circuit, in response to receiving said data request while an update to said selected storage medium is being performed, for servicing said data request by reference to said data and said related parity data of other storage media among said plurality of storage media.

26. A computer program product comprising:

a computer-readable medium;

updating code encoded within said computer-readable medium for receiving a data request for data stored by a selected storage medium among a plurality of storage media; and

request servicing code encoded within said computer-readable medium, in response to receiving said data request while an update to said selected storage medium is being performed, for servicing said data request by reference to data and related parity data of other storage media among said plurality of storage media.