Patent ID: 8117416

Claim:
A storage device, comprising: a virtual volume that provides a virtual storage area for a host device; a first pool area including a plurality of first storage devices; a second pool area including a plurality of second storage devices; and a controller configured to: assign one or more first storage region belonging to the first pool area to the virtual volume in response to receiving a write request from the host device, monitor a time zone history indicating an existence or non-existence of access to the first pool area, the second pool area and the one or more first storage region assigned to the virtual volume in each time zone, calculate a first similarity value on the basis of a time zone history of access to the first storage region assigned to the virtual volume and a time zone history of access to the first pool area, calculate a second similarity value on the basis of the time zone history of access to the first storage region assigned to the virtual volume and a time zone history access to the second pool area, if the first similarity value is lower than a first predetermined value, migrate a data in the first storage region to a second storage region belonging to the second pool area if the second similarity value is higher than a second predetermined value, and spin down the plurality of second storage devices in case where a time zone of no access to the second pool area including the second storage region.