In a method of operating a storage device, a first throughput, for transmitting a plurality of write command completion responses to an external host device, is set to an initial value. The plurality of write command completion responses represent an execution of a plurality of write commands received from the external host device. The plurality of write commands are executed. The plurality of write command completion responses are transmitted to the external host device based on the first throughput that is set to the initial value. A plurality of write data are internally stored based on the plurality of write commands. A second throughput, associated with an operation of internally storing the plurality of write data, is monitored during a predetermined first time interval. The first throughput is changed based on the second throughput that is monitored during the predetermined first time interval.