A data transfer method of a storage device which includes a host bus adaptor to communicate with an external host via a first interface and to communicate internally via a second interface is provided. The data transfer method may include issuing a write command and a read command to the host bus adaptor; performing a read direct memory access operation using the first interface in response to the write command and simultaneously performing a write direct memory access operation using the second interface in response to the read command; and generating frame information structure (FIS) sequences according to the second interface in response to the issued write command and the issued read command. The first interface may perform a full duplex data transfer and the second interface may perform a half-duplex data transfer.