A disk array device having a dual controller for executing data input/output processing for disk drives in response to a data input/output request from a host computer. Each controller constituting the dual controller has an FC controller which is interface-connected to the host computer via one path of a front interface connection FC and to the disk drives via one path of a back interface connection FC, and a PBC for switching the connection destination of the back interface connection FC betwe...

A storage system includes at least one storage medium, at least one controller to control the storage medium, and a communication path to connect the storage medium and the controller in a loop for communication between the controller and the storage medium, wherein a failure diagnosis is performed to locate a failure while performing normal read/write operations.

A storage system includes at least one storage medium, at least one controller to control the storage medium, and a communication path to connect the storage medium and the controller in a loop for communication between the controller and the storage medium, wherein a failure diagnosis is performed to locate a failure while performing normal read/write operations.