According to the present invention, each of a plurality of LUs existing on a storage control system 200 is divided into a plurality of chunks. A PVOL is comprised of only FC-chunks, but an SVOL is comprised of both FC-chunks and SATA-chunks. To each of the plurality of SVOL-chunks corresponding to the plurality of PVOL-chunks respectively, either an FC-chunk or SATA-chunk selected from a plurality of pool chunks is dynamically corresponded based on the update frequency of the sub-data of the corresponding PVOL chunk. Specifically, if an SVOL-SATA-chunk is corresponded to the PVOL-chunk of which the data update frequency is high, for example, the pool FC-chunk is corresponded as a sub-data swap destination in that SVOL-SATA-chunk.