A meta data server 100, a user node 200 and a storage device 300 are connected together via a Fibre channel 10 and a LAN 20 to configure a NAS over SAN system. The user node 200 sends out a request to access the data in each file. The file is stored in the storage device 300 in blocks of default size. The meta data server 100 informs the user node 200 of the block number where the file to be accessed is stored based on meta data in which relationship between a file and a block is recorded. Prior to this processing, the meta data server 100 instructs the storage device 300 to cache the data in advance. This application enables the storage device 300 to provide the data promptly in response to read request from the user node 200.