This storage system includes a first storage sub system having a first logical volume where a first data area is dynamically allocated to each prescribed area, and which stores data transmitted from a host computer in the first data area, and a second storage sub system having a second data area for backing up the first logical volume; wherein the first storage sub system includes: a first management unit for managing the status of the first data area allocated to each of the areas of the first logical volume; a transfer unit for transferring the data stored in the first data area allocated to each of the areas of the first logical volume to the second storage sub system; and a restoration unit for restoring the first logical volume based on the status of the first data area managed by the first management unit and/or the data transferred from the second storage sub system.