WD RE Enterprise SATA Hard Drives Ideal for enterprise servers and storage, video surveillance, and other write-intensive applications, WD RE 7200 RPM Enterprise SATA hard drives offer up to 4 TB capacity, 64 MB cache, 4th generation vibration tolerance and 5-year limited warranty. A head positioning system with two actuators that improves positional accuracy over the data track(s). The primary actuator provides coarse displacement using conventional electromagnetic actuator principles. The secondary actuator uses piezoelectric motion to fine tune the head positioning to a higher degree of accuracy.