To prevent for a prolonged time period, the fixed-position floating status of a head in the control operation of a storage unit, and to prevent a decrease in the reliability due to deterioration in the properties of a storage medium, a control apparatus is described. The control apparatus relays read/write instructions for a magnetic disk unit, and includes an access-area setting unit that dynamically specifies one of a plurality of unit areas provided in a magnetic disk storage area as an access area for data, an addressing unit that updates the value of a write address in a data write request with an address that represents a physical sector corresponding to an access area in the storage area, and a valid-area changing unit that migrates data to a sector in an access area from a physical sector in another unit area corresponding to the sector at predetermined time.