A storage device includes a data buffer, a device controller, and nonvolatile memories. The data buffer is configured to transact data from an external device. The device controller is configured to receive a command and an address from an external device, to control the data buffers, and to transact data with the data buffers. The nonvolatile memories are configured to perform write, read, and erase operations under control of the device controller. When a first link training between an external device and the data buffers is performed by the external device, the device controller performs a second link training between the device controller and a data buffer internally without control of the external device.