A first storage control system comprises a CHN connected to a LAN CN. The CHN comprises a NAS processor and I/O processor. The I/O processor judges whether all or a portion of block level data is to be stored in either a first storage control system or a second storage control system, on the basis of an I/O allocation control data which indicates which of either the first storage control system or the second storage control system the block level data is to be stored in. On the basis of the result of this judgment, the I/O processor transfers the block level data from the NAS processor, to at least one of the DKA and the CHF connected to the second storage control system.