A server computer, upon receiving a signal for a write request to a storage device from a management computer, performs a provisional write, which is a write related to the write request signal, to a first storage part in the server computer, and sends a first notification signal indicating that the provisional write has been completed to the management computer. The management computer, upon receiving the first notification signal, transmits a second notification signal indicating that the management computer has received the first notification signal to the server computer. The server computer, upon receiving the second notification signal, performs write processing to the storage device. Thereby, a failure caused by dual execution of write processing to the disk is prevented when transferring processing from a main server to an auxiliary server in a case where the main server fails with regard to processing accompanying writing to the disk.