This invention enables a disk subsystem that employs the FC-AL connection to grasp the operation status of each disk drive, quickly locate a disk drive that has failed, and promptly carry out blocking processing. In a disk subsystem including plural drive enclosures which store disk drives, and a disk controller which controls transfer of data stored in the disk drives between the drive enclosures and a host computer. The drive enclosures each comprise a backend switch which is connected to the disk drives and to the disk controller, the backend switch comprises a status monitoring port through which operation status of switch ports of the backend switch is outputted, and the disk controller monitors a fault of the switch ports through the status monitoring port.