A scale-out device to control a group of non-volatile memory devices from among a plurality of non-volatile memory devices at a data storage device, includes a buffer and a scale-out controller. The buffer is configured to store address mapping information for the group of non-volatile memory devices, the group of non-volatile memory devices being a portion of the plurality of non-volatile memory devices at the data storage device. The scale-out controller is configured to control operation of only the group of non-volatile memory devices according to the address mapping information stored at the buffer.