A storage system that administrates data to be mounted on a client terminal, the data being categorized into a plurality of generations, and that controls data in response to a request to mount data received from the client terminal. The storage system including a storage unit that stores a first generation that is currently under operation as operational data, a second generation that had functioned as the operational data as backup data, and a third generation that is to be in operation as standby data, and a switching unit that switches the first and the third generations such that the third generation is stored as the operational data, and the first generation is stored as the backup data, and that switches the first and the second generations such that the second generation is stored as the operational data, and the first generation is stored as the backup data.