To suppress heat generation as the factor of fault to a minimum while preventing the performance of data read from being dropped by writing one file so as to completely store it in one disk device and activating the disk device when an access request is generated.

A disk array device 1 is provided with a disk array controller 10 and plural disk devices 20. The disk array device 1 controls the plural disk devices 20 through the disk array controller 10 and performs the write and read of data to the prescribed disk device 20. Corresponding to the writing request of the file, the disk array controller 10 writes one file so as to completely store it in one disk device 20 and stops the disk devices 20 to which there is no access request. Then, when the access request is generated to any stopped disk device 20, that disk device 20 is activated.