A storage apparatus is provided that is capable of reducing data maintenance management costs with a performance that is both highly reliable and fast. The present invention is storage apparatus where an intermediary device is arranged between a controller and a plurality of disk devices of different performances arranged in a hierarchical manner. The controller unit carries out I/O accesses to and from the disk devices via the intermediary devices based on access requests sent from host apparatus. The intermediary device includes a power saving control function for the disk device and carries out operation control such as spin off and spin up of disk devices in accordance with conditions set in advance.