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Method and apparatus for the on-line restoration of a disk in a RAID-4 or RAID-5 array with concurrent access by applications

  • US 5,522,031 A
  • Filed: 06/29/1993
  • Issued: 05/28/1996
  • Est. Priority Date: 06/29/1993
  • Status: Expired due to Term
First Claim
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1. In a storage system having n+1 disks arranged in a RAID array, a plurality of data blocks, a plurality of parity blocks, each parity block associated with n data blocks, a plurality of status bits, each status bit associated with one of said data blocks or said parity blocks, each status bit having a first state indicating that said associated block may contain invalid information and a second state indicating that said associated block contains valid information, a method of on-line reconstruction of a new disk replacing a failed disk in said array while preserving concurrent access to said array by a user application, comprising the steps of:

  • detecting a failed disk in said array;

    removing said failed disk from said array;

    preparing a new disk by setting all status bits to said first state;

    adding said new disk to said array;

    systematically reconstructing data or parity blocks with associated status bits in said first state and after each reconstruction of a data block or parity block, setting said associated status bit to said second state;

    continuing said systematic reconstruction until all blocks on said new disk have been reconstructed;

    receiving requests to access data blocks in said new disk from said user application;

    writing data to said accessed data blocks in said new disk and setting said associated status bits to said second state whereby the most active portions of said new disk are reconstructed before other portions.

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