In a system including a plurality of rotatable media type memory devices and disk array storage including in a redundant configuration a plurality of controllers each including a disk array control unit in which a plurality of SCSI bus coupling ports are individually coupled with respective ports of a plurality of host PCs/WSs via SCSI cables, the disk array control unit includes a function to logically transmit a bus operation such as a device or bus reset operation in an arbitrary one of the ports of the disk array storage to other ports. This makes it possible that the ports seems to be physically coupled in a daisy chain when viewed from the host PCs/WSs.