It is an object of the present invention to conduct data transfer or data
copying between a plurality of storage systems, without affecting the
host computer of the storage systems. Two or more auxiliary storage
systems 100B, 100C are connected to a primary storage system 100A
connected to a host device 180. The auxiliary storage systems 100B, 100C
read journals of data update from the primary storage system 100A at
respective independent timings, save the journals in prescribed logical
volumes JNL 2, JNL 3, produce copying of the data present in the primary
storage system 100A based on the journals present in the logical volumes
JNL 2, JNL 3 at the independent timings, and save the copies in auxiliary
logical volumes COPY 1, COPY 3. The primary storage system 100A holds the
journals till both auxiliary storage systems 100B, 100C read the journals
and restore. The timing of journal read can be controlled according to
the journal quantity, processing load, and the like.