Following the introduction of 2TB hard drives The two internal hard drives use WD's GreenPower technology for power savings and cool and quiet operation. Connectivity interfaces include eSATA, FireWire 800, FireWire 400 and USB 2.0 and an accessible enclosure lets owners replace one or both drives without having to replace the entire array. The 4TB My Book Studio Edition II is available now for an estimated $650 and Western Digital is backing it with a generous five-year warranty.