Client 101 sends a function to be executed to server 102, and at the same time, sends information such as the send destination disk unit, function name, version, etc. The server stores the received function, uses the received information to create function information 127, creates function information 126 that contains access area list 124 to be sent to disk unit 103, and then sends the function and function information 126 to the disk unit. The disk unit stores the function and function information. When a function execution request is sent from the client to the server, if the server is also sent parameters, it creates additional function information 126 and sends said function information 126 together with the function execution request to the disk unit. The disk unit performs the function execution and restricts accesses during execution according to function information 126.