To provide a storage controller which reduces data-copying operations which are unnecessary, to improve reliability in backup, and to provide a storage system and a copying method.

The storage controller copies copy-source data stored in a copy-source volume to a copy-destination volume. In addition, the storage controller includes a copy-source data comparing part which compares data received from a host with data to which an area in a copy-source volume which stores the data received from the host is written; and a copying-function executing part which avoids writing the data received from the host to the copy-source volume, on the basis of the determination that these data compared by the copy-source volume comparing part accord.

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