Provided is a file server providing a file service to a host computer, including an interface coupled to the host computer; a processor; a memory; and an interface coupled to a disk drive. The file server is configured to calculate a capacity of storage areas in the memory, which is required to provide the file service; execute a first memory check in which the storage areas having the calculated capacity are tested; execute, after the first memory check is completed, a second memory check in which remaining storage areas in the memory are tested; and start, in a period after the first memory check is completed and before the second memory check is completed, providing the file service.