On Jul 26, 2005, at 6:26 PM, Rob Studdert wrote:
the heads rest on an air bearing when running. when not, they are
resting on the drive.
Not in any modern drive that I'm aware of. Any good modern drive's
head mechanism does a retract and lock when powered down.
Of the last 15 or so drives that I've dismantled (big server drives
to cheap
consumer drives old and new and all failed), none retract the
heads, they
simply park them at the centre (non-data area) of the platter. The
actuator arm
often has a physical lock but there is nothing preventing the disk
platter from
rotating against external forces (either direction) and damaging
the heads.
The 'retract and lock' of the head mechanism that I've seen is to
lift the heads several thousandths of an inch from the surface of the
platter. Platter rotation will do nothing to them. Vertical movement
of the platters could bang the heads, but generally they're
constrained to less than .001" vertical movement unless you subject
them to several Gs shock load.
Godfrey
