Patent ID: 9176882
Filing Date: 2015-11-03
Classification: G06F

Abstract:
1. A virtual tape device comprising: a storage unit that records logical volume information of a plurality of logical volumes, the logical volume information including, for each respective one of the plurality of logical volumes, an identifier of the respective logical volume, an updated time of the respective logical volume, information indicating whether the respective logical volume exists on a cache, an identifier of a respective physical volume storing data of the respective logical volume, and information indicating whether the respective physical volume is mounted in a physical tape drive; a cache determining unit that determines, based on the logical volume information, whether a requested logical volume exists on the cache when a request to store the requested logical volume on the cache is received and whether a logical volume, being updated and stored in the physical volume mounted in the physical tape drive, exists on the cache when the cache does not have available capacity; a selector that selects, based on the result of the determination made by the cache determining unit, the logical volume information, and a determination that the requested logical volume has been read into the cache from the physical volume at least a predetermined number of times, as a target logical volume to be offloaded from the cache, a logical volume of the plurality of logical volumes updated at an earliest time among logical volumes that exist on the cache; and a cache controller that offloads the target logical volume selected from the cache by the selector.