History (2009): WD Caviar Black 2TB 7,200rpm HDD

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2009: WD Caviar Black 2TB
Two stage actuation enables higher track pitch

Why it’s important
A two stage actuator separates the track to track motion into a coarse positioner and a fine positioner thereby lowering the mass of the fine positioniong mechanism which allows higher track pitch and thereby higher areal density.

Discussion
In 1983 Drivetec shipped a flexible media disk drive using a dual stage stepper/stepper design that read conventional and high tpi FDs (it used a coarse stepper driving a cantilevered beam carrying the second fine stepper positioning the head over the track).

First commercialization in HDDs announced as WD Caviar Black 2TB (model WD2001FASS) and WD RE4 2TB (model WD2003FYYS)

HGST announced a similar structure in 2013.