A storage system comprising: - a first storage device, configured to be installed in a first site, including a first adapter and a first cache memory and providing a primary logical volume in which data received from a host computer via the first adapter and the first cache memory is written; - a second storage device, configured to be installed in a second site, including a second adapter and a second cache memory and providing a virtual logical volume, which has no substance for storing data received from the first storage device via the second adapter and the second cache memory; and - a third storage device, configured to be installed in a third site, including a third adapter and a third cache memory and providing a secondary logical volume in which data received from the second storage device via the third adapter and the third cache memory is written, - wherein data written in the primary logical volume of the first storage device are remote-copied to the secondary logical volume of the third storage device via the virtual logical volume of the second storage device, the data being written in the same location as the primary logical volume within the secondary logical volume of the third storage device; characterized in that when the storage system stops the remote-copy between the second storage device and the third storage device, the first storage device does not transmit data to be remote-copied to the virtual logical volume of the second storage device, and each of the first storage device, the second storage device and the third storage device manages a respective bit map indicating an address location of each of one or more data, each of the one or more data being held by the respective storage device (4A; 4B; 4C) as data to be remote-copied/written to the secondary logical volume of the third storage device; and when the storage system resumes the remote-copy from the primary logical volume of the first storage device to the secondary logical volume of the third storage device via the virtual logical volume of the second storage device, a first merged bit map indicating a plurality of the address locations managed by the first storage device, the second storage device and the third storage device is obtained by merging, after obtaining a second merged bit map being obtained by merging the bit maps managed by the second storage device and the third storage device at the second storage device, the bit map managed by the first storage device and the second merged bit map at the first storage device, and data corresponding to each of the address locations indicated in the first merged bit map is transmitted from the primary logical volume of the first storage device to the secondary logical volume of the third storage device via the virtual logical volume of the second storage device. - a first storage device, configured to be installed in a first site, including a first adapter and a first cache memory and providing a primary logical volume in which data received from a host computer via the first adapter and the first cache memory is written; - a second storage device, configured to be installed in a second site, including a second adapter and a second cache memory and providing a virtual logical volume, which has no substance for storing data received from the first storage device via the second adapter and the second cache memory; and - a third storage device, configured to be installed in a third site, including a third adapter and a third cache memory and providing a secondary logical volume in which data received from the second storage device via the third adapter and the third cache memory is written, - wherein data written in the primary logical volume of the first storage device are remote-copied to the secondary logical volume of the third storage device via the virtual logical volume of the second storage device, the data being written in the same location as the primary logical volume within the secondary logical volume of the third storage device;