This invention provides a control technique of a data processing system, in which functions of a highly-functional high-performance storage system are achieved in an inexpensive storage system so as to effectively use the existing system and reduce the cost of its entire system. This system has a RAID system, an external subsystem, a management server, a management client and the like. The management server includes an information management table for storing mapping information of the RAID system and the external subsystem. When performing copy process, the pair creation in which a logical volume of the RAID system is set as a primary volume of copy source and a logical volume of a mapping object of the RAID system mapped from the logical volume of the external subsystem is set as a secondary volume of copy destination is executed from the management client by using the information management table.