Hard Drives
WD RE4 - 500GB 3.5-inch Enterprise SATA Hard Drive - OEM
Dual Actuator technology - a head positioning system with 2 actuators that improves positional accuracy over the data tracks StableTrac - the motor shaft is secured at both ends to reduce system-induced vibration and stabilize platters for accurate...
https://www.bizrate.co.uk/harddrives/wd-re4-500gb-3-5-inch-enterprise-oid2327251570.html