Data storage control on storage devices

摘要

An object of the present invention is to improve the usage efficiency of a storage extent in a storage system using the Allocation on Use (AOU) technique. A controller in the storage system allocates a storage extent in an actual volume to an extent in a virtual volume accessed by a host computer, detects any decrease in necessity for maintaining that allocation, and cancels the allocation of the storage extent in the actual volume to the extent in the virtual volume based on the detection result.