A controller sets, out of a data range that is specified in a read request from a host device, a predetermined size of a first data range that follows a top portion of the data range and a predetermined size of a second data range that follows the first data range, and after transfer, to the host device, of data corresponding to the first data range from a second storage unit or a third storage unit having smaller data output latency than the first storage unit in which read/write of data is performed is started, the controller searches for data corresponding to the second data range in the second storage unit or the third storage unit.