A computer system including: a computer having a display to display information of a plurality of backup times, and an inputting device by which a user selects a backup time of the plurality of backup times; and, a storage system coupled to the computer and having an interface controller receiving data from the computer, a cache memory temporarily storing data and a disk controller managing data for at least one volume related to a plurality of disk drives; wherein the computer system causes the computer to make a snapshot corresponding to the selected backup time accessible with an address to which the computer can access.