A control method comprising: a first step of detecting, by the server module, a failure in the first interface; a second step of executing, by the server module, given recovery processing when a failure is detected in the first interface; a third step of using, by the coupling module, the first end point to detect a failure in the first interface and output a failure notification; a fourth step of converting, by the coupling module, the failure notification into a notification of disconnection of the first interface, and transmitting the disconnection notification generated by the conversion to the storage module from the second end point; and a fifth step of disengaging, by the storage module, coupling to the server module when the disconnection notification is received from the coupling module.