Patent ID: 8161317

Claim:
A storage system, comprising: a plurality of disk drives storing data used by a host computer; a disk controller configured to control data access to said disk drives, providing a plurality of storage layers configured by said disk drives, and controlling to change a power mode of said disk drives from an access mode in which said disk drives are operating to write data to a power saving mode; a power supply controller configured to autonomously turn off a power source of at least one of said disk drives according to said disk controller, and autonomously turn on the power source of said disk drive which was turned off, after the lapse of a prescribed period from the time said power source was turned off, irrespective of data access status to said disk drive which was turned off in order to inspect by an inspection process a failure in said disk drive; wherein said disk controller controls the inspection process of said disk drive which was turned off corresponding to each storage layer; and wherein said power supply controller selects said disk drive for turning on the power source irrespective of the data access status to said disk drive based on a predefined policy.