According to one embodiment, a controller writes first data into a first storage area in accordance with a first write command from a host. The controller identifies a logical address mapped to the written first data. The controller writes internal data that is read from a second storage area into a first location of the first storage area. The controller associates the first storage location with the logical address. The controller reads the internal data from the first storage location in response to receiving, from the host, a read command that designates the logical address. The controller transmits, to the host, the internal data read from the first storage location.