A data processing apparatus includes a first memory that has first storage areas, a capacity of each first storage area being variable, a second memory that has second storage areas, a capacity of each second storage area being variable, and each second storage area is redundant to a first storage area corresponding to a second storage area, a memory controller that stores data stored in each first storage area to the corresponding second storage area, and writes data stored in a second storage area to the corresponding varied first storage area and writes data stored in a first storage area to the corresponding varied second storage area when capacities of the first storage area and the second storage areas are varied.