A data storage device includes a first controller; a scale-out storage device; and an interface connected between the first controller and the scale-out storage device, wherein the first controller is configured to transmit, to the scale-out storage device through the interface, a first command including a command type and command information having a parameter with respect to the command type, wherein the scale-out storage device is configured to perform an operation corresponding to the first command, and wherein the scale-out storage device includes, a scale-out controller connected to the interface, a volatile memory connected to the scale-out controller, and a non-volatile memory connected to the scale-out controller.