A storage system includes a storage controller, plural volumes each configured by the storage controller, and a pool allocating physical storage areas to logical storage areas of the volumes. The storage controller configures a first group including, among the volumes, a first primary volume to which a first target protection period is set, and a first history information volume storing history information about updating to the first primary volume, and a second group including, thereamong, a second primary volume to which a second target protection period is set, and a second history information volume storing history information about updating to the second primary volume. The volumes included in the first and second groups utilize the same physical storage area of the pool. When increasing a free capacity thereof, history information to be purged is determined from the first and second protectable periods such that their protectable periods become the same.