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Method and apparatus for de-duplication after mirror operation

  • US 20080244172A1
  • Filed: 03/29/2007
  • Published: 10/02/2008
  • Est. Priority Date: 03/29/2007
  • Status: Active Grant
First Claim
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1. A method of operating an information system, comprising:

  • storing data to a first storage volume and mirroring the data to a second storage volume, said second storage volume being a virtual volume having a plurality of logical storage addresses, wherein a segment of physical storage capacity is allocated for a specified logical address as required when the data is to be stored to said specified logical address;

    selecting segments of the second volume during a de-duplication operation on the second volume;

    calculating a hash value for a particular segment representative of the data contained in the particular segment;

    comparing the calculated hash value with previously-stored hash values for other segments in the second volume;

    linking the particular segment to another segment having a previously-stored hash value that matches the calculated hash value of the particular segment; and

    releasing the particular segment from the second volume when another segment has a previously-stored hash value that matches the calculated hash value of the particular segment, whereby physical storage capacity required for the second volume is reduced.

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