Abstract: A RAID controller has a host IDE interface and a disk array IDE interface respectively adapted to connect to a host system and a disk array. Both the specifications of the IDE interfaces are chosen as parallel transmission mode or series transmission mode. The RAID controller further has a CPU, a process control unit, a buffer memory unit and a program memory unit, wherein the program memory unit is stored with programs and commands to implement RAID level 3, level 4, level 5 and level 6 technology so as to control the process control unit to process data stored in the buffer memory unit.