An electronic device may include a plurality of data storage devices including a master storage device and one or more slave storage devices. Each of the data storage devices comprises a storage configured to store data and a controller configured to control data input/output operations with respect to the corresponding storage. The controller of the master storage device receives device information including identification information, capacity information and physical configuration information from each of the slave storage devices, and the controller of the master storage device changes an electric power mode of at least one of the slave storage devices selected based on capacity margin of the master storage device and the device information.