There is provided a storage system suitable for an open system which has advanced security functions for logical devices. In a storage system such as a RAID system, 6 types of access attributes which are Readable/Writable, Read Only, Unreadable/Unwritable, Read Capacity 0, Inquiry Restricted, and S-vol Disable, can be set for each logical device. Read Capacity 0 makes a response "capacity 0" upon inquiries from hosts about capacity. Inquiry Restricted does not permit the hosts to recognize logical devices. S-vol Disable does not permit pair forming for duplication of a logical device with another device as the destination of copying. Upon receipt of commands from hosts of the open system, the storage system changes command processes and responses, depending on the difference in operation system, vendor, version, or the like, between hosts.