The TOP bay of this Firewire 800 desktop unit is READ/WRITE. The BOTTOM bay is READ ONLY.Connection to the host system is via a Firewire800 (IEEE 1394b) interface which supports data fransfer speeds of up to 800Mbps.The drive bays have 48Bit interfaces and support hard disks bigger than 128Gb drives making this unit ideal for fast lab basedimaging and analysis duties.