A receiving controller which receives a read request out of first and second storage controllers transfers the read request to an associated controller which is associated with a read source storage area out of the first and second storage controllers when the receiving controller is not the associated controller. It is however the receiving controller that reads the read-target data from a read source storage device, writes the read-target data to a cache memory of the receiving controller, and transmits the read-target data written in the cache memory of the receiving controller to a host apparatus.