RTII3DAR5 RAID Tower II (black color) with 1 4X1 eSATA/USB 2.0 Hardware Port Multiplier installed. Install up to three 3.5" SATA hard drives of any capacity. Drives are installed onto drive tray that can be added or removed like tape cartridge from each drive bay. Connect to system via USB 2.0 or eSATA port (connecting cables included). Drives can be configured as FAST2 (2 drive RAID 0 Striping),, SAFE2 (2 drives RAID1 Mirroring), BIG 2 (2 drives Concatenation), 3 drives in RAID 3, or 3 drives in RAID 5. RAID setting via a rotary switch on the back. OS independent, can be used on any system. Optional 4th drive can be attached via the eSATA port on the back using external eSATA drive.