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Fast updating of DASD arrays using selective shadow writing of parity and data blocks, tracks, or cylinders

  • US 5,375,128 A
  • Filed: 10/18/1990
  • Issued: 12/20/1994
  • Est. Priority Date: 10/18/1990
  • Status: Expired due to Fees
First Claim
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1. A method for reading and update writing of parity groups of data and explicit parity blocks across an array of DASDs in a reduced number of DASD rotational track cycles, comprising the steps of:

  • (a) distributing the data and parity blocks for each parity group across the DASDs in the array in failure independent form and reserving unused DASD space; and

    (b) amending at least one data block in a preselected parity group resident on said array by;

    (1) during a first rotational track cycle, reading the said at least one data block and the parity block of the preselected parity group from said array; and

    (2) during a second rotational track cycle,(i) calculating a new parity block,(ii) shadow writing at least the new parity block into the reserved unused space nearest in rotational relation to the location of said data block, and(iii) writing an amended data block in place of said one data block.

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