A storage apparatus includes multiple ports communicable with a server, multiple processor cores and multiple LUs (Logical Units). For each port, a port responsible core, which is a processor core to accept an I/O request received by the port, is specified. For each LU, an LU responsible core, which is a processor core responsible for I/O, is specified. The LU responsible core may be dynamically changed. The server periodically acquires identification information about the LU responsible cores from the storage apparatus. When transmitting an I/O request, the server selects a non-cross call path, which is such a path that the LU responsible core and the port responsible core are the same processor core, from among multiple paths to an I/O destination LU, which is an LU specified by the transmission target I/O request, and transmits the transmission target I/O request via the selected path.