Digital data storage system with improved data migration

United States Patent t^j

Kenley et al.

US005276867A

[i i] Patent Number: [45] Date of Patent:

5,276,867 Jan. 4, 1994

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(List continued on next page.)

Primary Examiner—Paul V. Kulik

Attorney, Agent, or Firm—Lahive & Cockfield

A digital data storage apparatus has primary, secondary and backing storage elements characterized by respectively longer access times. A level detector signals when the quantity of data in the secondary store exceeds a threshold amount. A data migrator responds by moving selected data files from the secondary store to the backing store. The apparatus also includes a baseline back-up element that stores archive copies of a set of selected data files. A full back-up element stores archive copies of those files that, (1) were originally copied to the baseline back-up set but have since changed, or (2) are not otherwise within the baseline back-up set. For those files which were originally copied to the baseline back-up set and which have not changed, the full backup element stores pointers indicating locations of the respective files in the baseline back-up set.

35 Claims, 5 Drawing Sheets

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OTHER PUBLICATIONS

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