Dual Stage Actuator HDDs Appear on WD SATA HDDs

To read this article from Gerson Lehrman Group, click on:
Dual Stage Actuator HDDs appear on SATA disk drives
By Tom Coughlin

Summary
Western Digital announced that their new 2 TB 7,200 RPM Caviar HDDs use dual actuators.  Dual (actually dual-stage) actuators provide a coarser movement of the recording head to tracks using head arms moved by a conventional voice coil motor while a finer motion is provided using a piezoelectric actuator closer to the head.  Dual stage actuators add some cost to the drive and increase servo control complexity but allow higher track density recording.  Dual stage actuators had only appeared in some enterprise (high performance) HDDs from Seagate and other companies in that market to this point.