In a disk controller having a plurality of controller modules (CMs), the CM includes a path obstruction determination unit for obstructing a part in which an anomaly occurs when the anomaly occurs on a communication path for communications between CMs, and, when the plurality of CMs cannot communicate between them due to the obstruction of the part, for determining an object to be separated in a way that prioritizes a CM which retains data that has not been duplicated over a CM which retains data that has been duplicated among the CMs which cannot communicate; and a separation control unit for disabling a CM that is determined to be an object to be separated by the path obstruction determination unit.
