Patent 10089027 was granted and assigned to Toshiba Memory Corporation on October, 2018 by the United States Patent and Trademark Office.
According to an embodiment, when a storage status of a first storage unit is recognized as a protected state, a control unit writes data to a second storage unit. When a read target address is recorded in a data migration log area, the control unit reads data from the second storage unit. When the read target address is not recorded in the data migration log area, the control unit reads data from the first storage unit.