A storage device includes a buffer memory configured to temporarily store data; a plurality of nonvolatile memory devices; a storage controller circuit configured to generate buffer memory status information by monitoring a status of the buffer memory and operating in a congestion control mode of setting a buffer memory data transmission authority of a nonvolatile memory based on the generated buffer memory status information; and a first interface circuit configured to communicate with the storage controller circuit and the plurality of nonvolatile memory devices, wherein the first interface circuit is connected to a network based on an Ethernet interface.