Abstract: A file server has plural NAS nodes having three processors dispersed in function, a shared cache memory shared between the plural NAS nodes and backed up by a battery, and plural storage devices. A log area for storing data with respect to an access request received by each NAS node is arranged in the shared cache memory. A network processor stores the data with respect to the access request to the log area, and transfers the data of the memory by a DMA at a reading time. Even when a failure is happened in a certain NAS node, another NAS node restores a file system using the log and continues processing to store the data with respect to the access request to the shared cache memory.