Error detection in redundant array of storage units

• US 20050066254A1
• Filed: 09/10/2004
• Published: 03/24/2005
• Est. Priority Date: 09/24/2003
• Status: Abandoned Application

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Maddock, Robert Frank, Grainger, Bernard John
• Application Number:
  US10/938,278
• Publication Number:
  US 20050066254A1
• Time in Patent Office: Days
• US Class Current: 714/764
• CPC Class Codes: G11C 29/24 Accessing extra cells, e.g. dummy cells or redundant cells

Abstract

A storage controller (160) and method (200) for error detection in disk arrays (150) with multiple redundancy by: receiving from each of the disks in the array a linear XOR value derived from data in a desired segment of the unit; comparing the received values from the different disks; and determining, responsive to the comparison, an error in data from one of the disks. Scrubbing is completed by reconstructing, responsive to the error determination, the erroneous data and re-writing it to the erroneous segment. This allows detection of data errors where prior art could not, and detects these errors without a significant increase in controller-disk link data traffic.

Claims

1. A storage controller for error detection in an array of a plurality of storage units, comprising:

a receiving unit to receive from a plurality of the storage units in the array a value derived from data in a desired segment of the storage unit;

a comparing unit to compare the received values from different storage units; and

an error determining unit, responsive to the comparing unit, to determine an error in data from one of the storage units.

2. The storage controller of claim 1 wherein the value derived from data in a desired segment of the storage unit is a linear XOR logic combination of the data.

3. The storage controller of claim 1 wherein the array is a multiply redundant array.

4. The storage controller of claim 1 wherein the storage units comprise disk drives.

5. The storage controller of claim 1 further comprising a reconstruction unit, responsive to the error determining unit, to reconstruct erroneous data and to re-write the reconstructed erroneous data to an erroneous segment.

11. An integrated circuit comprising the storage controller of claim 1.

6. A method of error detection in an array of a plurality of storage units, comprising:

receiving from a plurality of the units in the array a value derived from data in a desired segment of the unit;

comparing the received values from the different units; and

determining, responsive to the step of comparing, an error in data from one of the units.

7. The method of claim 6 wherein the value derived from data in a desired segment of the unit is a linear XOR logic combination of the data.

8. The method of claim 6 wherein the array is a multiply redundant array.

9. The method of claim 6 wherein the storage units comprise disk drives.

10. The method of claim 6 further comprising reconstructing, responsive to the step of determining an error, the erroneous data and re-writing it to the erroneous segment.

12. A storage controller for error detection in an array of a plurality of storage units, comprising:

means for receiving from a plurality of the units in the array a value derived from data in a desired segment of the unit;

means for comparing the received values from the different units; and

means, responsive to the means for comparing, for determining an error in data from one of the units.

13. The storage controller of claim 12 wherein the value derived from data in a desired segment of the unit is a linear XOR logic combination of the data.

14. The storage controller of claim 12 wherein the array is a multiply redundant array.

15. The storage controller of claim 12 wherein the storage units comprise disk drives.

16. The storage controller of claim 12 further comprising means, responsive to the means for determining an error, for reconstructing the erroneous data and for re-writing it to the erroneous segment.

17. A signal bearing medium tangibly embodying a program of machine-readable instructions executable by a digital processing apparatus to perform operations to detect data errors in a redundant storage system comprised of an array of storage units, the operations comprising:

receiving from a plurality of the storage units in the array a value derived from data in a desired segment of the storage unit;

comparing the received values from different storage units; and

determining, responsive to comparing, an error in data from one of the storage units.

18. A signal bearing medium as in claim 17, where the value derived from data in a desired segment of the storage unit is a linear XOR logic combination of the data.

19. A signal bearing medium as in claim 17, where the array is comprised of a multiply redundant array of disk drives.

20. A signal bearing medium as in claim 17, further comprising reconstructing, responsive to determining an error, the erroneous data and re-writing it to an erroneous segment.

21. A disk controller coupled to at least one controlled disk, comprising circuitry coupled to an external data processor via a bus, said circuitry responsive to a receipt over the bus of a predetermined type of read command to read a specified segment of data from the at least one controlled disk, to determine a value of an Exclusive OR operation performed on data read from the specified segment, and to return to said external data processor over said bus the determined value.

22. A storage array controller coupled to at least one disk controller that is coupled to a plurality of controlled disks, said storage array controller comprising circuitry, coupled to said at least one disk controller via a bus, to issue a predetermined type of read command over the bus to the at least one disk controller to read a specified segment of data from the plurality of controlled disks, said at least one disk controller comprising circuitry responsive to a receipt of the read command to determine a value of an associate logical combination operation performed on data read from the specified segment on each of the plurality of controlled disks and to return a plurality of said determined values to said storage array controller over said bus, said storage array controller circuitry further being responsive to a receipt of said plurality of returned determined values to determine if the plurality of returned determined values are consistent and, if they are determined to be inconsistent, to initiate a data reconstruction operation for a segment determined to be a cause of the inconsistency.

23. A storage array controller as in claim 22, where the associate logical combination operation is comprised of a linear Exclusive OR operation performed on bytes read from the specified segment.

24. A storage array controller as in claim 22, where at least one of the controlled disks comprises a part of a parity disk drive.

25. A storage array controller as in claim 22, comprising a part of a RAID data storage system.