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Row-diagonal parity technique for enabling efficient recovery from double failures in a storage array

  • US 6,993,701 B2
  • Filed: 12/28/2001
  • Issued: 01/31/2006
  • Est. Priority Date: 12/28/2001
  • Status: Active Grant
First Claim
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1. A method for enabling recovery from two or fewer concurrent failures of storage devices in a storage array, the method comprising the steps of:

  • providing the array with a predetermined number of storage devices, including a plurality of first devices configured to store data and row parity, and one diagonal parity device configured to store diagonal parity, wherein the predetermined number of storage devices n is p+1 and wherein p is a prime number;

    dividing each device into blocks;

    organizing the blocks into stripes that contain a same number of blocks in each device, wherein each stripe comprises n−

    2 rows of blocks;

    defining the diagonal parity along diagonal parity sets that span the first devices, wherein the diagonal parity sets wrap around within a group of n−

    2 rows so that all blocks belonging to diagonal parity sets of a stripe are stored in the stripe; and

    computing and storing the diagonal parity for all of the diagonal parity sets except one on the diagonal parity device.

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