An apparatus includes a first storage unit for storing data received from the upper-layer apparatus in the first storage unit, a second storage unit, a data transmitting unit for transmitting the data stored in the first storage unit to the second storage apparatus based on an order that the data is stored in the first storage unit, a transferring unit for transferring and storing transfer data stored in the first storage unit into the second storage unit when an amount of the data stored in the first storage unit is larger than a predetermined amount, the transfer data being at least part of the data stored in the first storage unit; and, a staging unit for transferring the transfer data stored in the second storage unit into the first storage unit if an amount of the data stored in the first storage unit is smaller than a predetermined amount.