Sans Digital RAID Enclosures(ER104UT+) Drive: SATA 150 & 300 External I/O: USB 3.0 (backward compatible with USB 2.0) and eSATA 3.5" Drive Bays: 4 x Hot-Swappable Power Supply: 220W 80PLUS; Auto switch for 100V~ 240V; 50 ~ 60Hz Redundant power supply option available Form Factor: Rackmount Maximum Capacity: 12TB Cooling Fan: 4 x Internal Control Interface: RAID Switch