Memory system having a plurality of interfaces as well as data access method in such a storage system

A hybrid storage system that has both SAN and NAS interface can be implemented by simple hardware which executes a SAN function independently of a NAS function and a NAS-load. More specifically, has a controller (110) of the storage system (100) via a NAS controller (145) for accepting an output for a file unit I / O command and a SAN controller (140) for accepting an output for a block unit I / O command. The NAS controller converts an output for a file unit I / O command in a command issued for a block unit I / O command, and transmits the issued for a block unit I / O command to the SAN controller. The SAN controller makes an access to a disk device in accordance with a stored data received from the SAN I / O command or a signal output from the NAS controller for a block unit command. The NAS and SAN controllers can operate independently.