A server system has servers that can be operated through switching as a primary system and a standby system, and a shared disk unit for storing data accessed by the servers. Each of the servers has a driver that acquires information on a configuration inside the shared disk unit after starting of the system. The driver sets the shared disk unit in an active state in which an access request can be sent to the shared disk unit. Access control determines whether the access request issued by an application should be sent on the basis of a management table indicating inhibited types of access requests for each access destination. The access control sends the access request to the driver when the access request is not inhibited for an access destination of the access request. By this arrangement, hot standby switching processing can be performed at high speed.