1. A data transfer system, comprising: a user process space where a plurality of user processes are executed; a kernel space comprising a kernel thread; and a hardware space performing an input/output according to the input/output request of the each user process, wherein when input data based on the input request are received to the hardware space, the data transfer system checks whether the user process requesting the input is in an execution state, and allows the kernel thread to copy the input data from the kernel space to the user process space when the user process is in the execution state.