Provided is a storage apparatus operable to prevent incomplete backup and perform efficient backup even in systems characterized by a relatively small backup window and high degrees of utilization by users. This storage apparatus performs a snapshot of a volume storing data, using a logoff or login request at a certain point in time within in the backup window as a trigger, and creates a replication volume of the volume based on the acquired snapshot. To achieve the data consistency, when a login request is made, the storage apparatus temporarily suspends processing for establishing a session until the snapshot is created, and resumes such processing for establishing the session based on a login request after the snapshot is created. In one implementation, the replication volume is created in the background.