In a storage system, a logical volume is divided into a plurality of small areas called logical storage devices and only such an area designated by a user is made an object of remote copying or migratory copying. Also, there is provided a unit for forming a logical volume from any logical storage device of any RAID group. Thereby, the reduction of the deterioration in performance at the time of remote copying, the reduction of a storage area to be assigned to a secondary site as a copy destination, the shortening of a time required for migratory copying and the assignment of any area of a logical volume on any RAID group are enabled.