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Apparatus-and-method-for-providing-data-redundancy-and-reconstruction-for-redundant-arrays-of-disk-drives

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Details

Inventors: Hashemi, Ebrahim; Schulze, Martin E.;
Assignee: Hitachi Computer Products America, Inc. (Santa Clara, CA)
Primary Examiner: Beausoliel, Jr.; Robert W.
Assistant Examiner: Elmore; Stephen C.
Attorney, Agent or Firm: Flehr Hohbach Test Albritton & Herbert LLP

The present invention provides a system of hardware and software that combine to form a redundant array of disk drives. This array provides a double means of redundancy that can reconstruct data from two simultaneously failed disks. The double redundancy means is implemented by two separate algorithms, DRR1 and DRR2. DRR1 takes the exclusive-or of all the commercial data and stores the result as redundancy data. DRR2 is similar to the algorithm described in Patel's article. As an additional feature, the implementation of DRR1 and DRR2 in the present invention is flexible enough to support either on-the-fly or read-modify-write level operation. Although both algorithms are in the prior art, the present invention improves on the run-time and space requirements of the algorithm. This improvement arises because of a novel relationship, discussed below, that exist between the individual T.sup.1 matrices and their column vectors that allows for a savings in computing the mapping of the commercial data to the redundancy data. This unique relationship is incorporated into the present systems hardware and software.

DETAILED DESCRIPTION The present invention provides a system of hardware and software that combine to form a redundant array of disk drives.
This array provides a double means of redundancy that can reconstruct data from two simultaneously failed disks.
The double redundancy means is implemented by two separate algorithms, DRR1 and DRR2.
DRR1 takes the exclusive-or of all the commercial data and stores the result as redundancy data.
DRR2 is similar to the algorithm described in Patel's article.
As an additional feature, the implementation of DRR1 and DRR2 in the present invention is flexible enough to support either RAID 4 or RAID-5 level operation.
Although both DRR1 and DRR2 algorithms are in the prior art, the present invention improves on the run-time and space requirements of the algorithm.
This improvement arises because of a novel relationship, discussed below, that exist between the individual T.
sup.
i matrices and their column vectors that allows for a savings in computing the mapping of the commercial data to the redundancy data.
This unique relationship is incorporated into the present systems hardware and software.

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