To provide a file transfer method and system capable of making backups in a unified manner at backup sites and MSP (Management Service Provider) operating under an around-the-clock system with high reliability equipment. When data to be transferred such as backup is transferred between SAN (Storage Area Network) storing units to back up the data stored in the SAN, a data transfer instruction is sent to the transfer source and transfer destination of the data transfer via a network which is different from the SAN.