There are two classes of scheduling policy: a first class in which a completion of data transfer requested by a data transfer request within a deadline for completing the requested data transfer, specified for the request, is a primary key factor in determining an order of processing, and a second class in which a reduction of amounts of mechanical actions of a storage device required in carrying out the data transfer requested by the request is a primary key factor in determining the order of processing. Data transfer requests with respect to the storage device are sequentially accepted. Each data transfer request is classified into the second class while the current time has not yet exceeded a time earlier by a certain time than the deadline. Each data transfer request is classified into the first class after the current time has already exceeded the time.