Computer system, and a computer system control method

A computer system according to the present invention includes a server and a storage device equipped with two controllers. The server is connected to the two controllers, and includes a sorting module with the function of transferring an I/O request with respect to the storage device to either of the two controllers. The sorting module, upon reception of the I/O request from an MPU of the server, reads I/O request transmission destination information from a sort table stored in the storage device, and, based on the transmission destination information that has been read, determines to which of the two controllers the I/O request should be transferred, and transfers the I/O request to the determined controller.