A copy source storage controller received write data added with a time and issued from a host computer transfers the write data with the time to a copy destination storage controller. If there are a plurality of copy destination storage controllers, a representative copy destination storage controller compares times of write data copied to the plurality of copy destination storage controllers, and writes the write data in copy destination logical volumes in the sequential order of time. The representative copy destination storage controller judges that integrity of the write data is established, if a communication procedure is established with the copy destination storage controller and if the statuses of the copy source/destination logical volumes are coincident. In remote copy which guarantees integrity of write data and traverses a plurality of storage controllers, it is possible to judge at an optional time point whether integrity of write data can be guaranteed.