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Restore method for backup

  • US 20050240813A1
  • Filed: 06/15/2004
  • Published: 10/27/2005
  • Est. Priority Date: 04/08/2004
  • Status: Active Grant
First Claim
Patent Images

1. An image restore method executed in a storage system comprising:

  • a disk array storage system comprising a disk drive in which a primary volume used by a server for some purpose is set from/to which data is read and written, a block device interface that sends and receives data and control signals to/from a computer, a disk interface that sends and receives data and control signals to/from with the disk drive, a memory that stores a control program, and a CPU that executes the control program to control input and output of the data to/from the disk drive; and

    a backup management device that manages backup and restore of the data stored in the disk array storage system using a full backup image obtained by copying a whole of the data stored in the primary volume at a predetermined timing and each delta image obtained by copying a data changed after one of the full backup and delta backup, the image restore method comprising;

    creating a temporary restored image by applying each required delta image to the full backup image and storing the temporary restored image in a restore destination volume;

    judging whether the reverse delta image and a cost table of applying delta relating to each applied the delta image have been created, with each reverse delta image recording the reverse delta image before the application of the applied delta image and the cost table of applying delta recording a number of blocks of the applied delta image;

    creating, if the reverse delta image and the cost table of applying delta relating to the applied delta image are not yet created, the reverse delta image related to the applied delta image and recording a number of delta application blocks relating to the applied delta image in the cost table of applying delta;

    judging whether an intended restore target has been restored with reference to a backup creation date and time recorded in a delta backup management table;

    recording, if it is judged that the intended restore target has been restored, a backup date and time of the restore target; and

    creating, if it is not judged that the intended restore target has been restored, a new temporary restored image, calculating a sum of a number of blocks of each reverse delta image that should be applied to the temporary restored image in order to reach the intended restore target with reference to the cost table of applying delta, and obtaining a number of blocks that is changed when restore is performed by applying the reverse delta image;

    calculating a sum of a number of blocks of the full backup image and a total number of blocks of each delta image that should be applied to the full backup image in order to reach the intended restore target with reference to the cost table of applying delta, and obtaining a number of blocks that is changed when the restore is performed by applying the delta image;

    comparing the number of blocks that is changed when the restore is performed by applying the reverse delta image with the number of blocks that is changed when the restore is performed by applying the delta image;

    performing the restore by applying the reverse delta image that is necessary in order to reach an intended restore target, to the temporary restored image if the restore through the application of the reverse delta image results in a fewer number of blocks to be changed; and

    performing the restore by sequentially applying the delta image that is necessary in order to reach an intended restore target, to the full backup image if the restore through the application of the delta image results in a fewer number of blocks to be changed.

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