In alt.comp.hardware.pc-homebuilt "Trimble said:
Thanks for your answer.
But common sense (for what that's worth
would assume the system disc
with frequent head / access activity will have greater wear & shorter
life than a 2nd ary Disc holding only some times accessed data.
Actually, "common sense" is completely *wrong* in this regard.
As I recall, from actual testing, the drives constantly random-accessed
to-death lasted *longer* than those just spinning on one track; and
those drives lasted *far* longer than those spun up and down on a
regular basis. The extra wear on the bearings of the arm being almost
unnoticeable compared to the problems of head-disk interface wearing on
the surface. Actual reading and writing or head-switching being all
electronic; and having no effect at all on lifetime.
But I note my various HD's in my home comp all seem to feel warm to the
touch regardless of weather they are being accessed.
Of course. The main heat of a drive is caused by the spinning disk,
*not* the access. With today's faster spinning drives, that means more
heat. Oh, *some* percentage of heat is added when seeking; as the
energy to move the actuator at a reasonable speed has to go *somewhere*.
So, to keep the heat down (and thus the lifetime longer) what you
*really* need is something that moves the actuator around on the drive
at a reasonably slow rate.
Of course, drive manufacturers *know* this; and most drives these days
have logic that watches how long it has been since the drive was last
accessed through the interface; and when it gets more than so long
(about ten minutes is my guess) they start moving the head/arm around on
the drive to keep it from wearing a hole in the lubrication on one track
.... That being the main problem these days with letting a head sit in
one spot for too long. Eventually the pressure forces the oil (or
equivalent) to spread out to adjacent tracks ... Thus making a ripple in
the surface and creating other problems as well.
The things most people know about disk-drives that just ain't so ....
Like shutting them off to increase their life-span. ;-{
Well ... It's just "common sense", isn't it?
Only, like I said, "common sense" doesn't know squat about modern
disk-drives. Ask the guys (like me) who test them to death, *trying* to
break them before a customer ever sees one. (Well ... OK ... I *used*
to be in that business.)
As I recall, about 90% or more of problems encountered that lead to
drives crashing or dying in one manner or another, were all head/disk
interface related. Less that 10% being electronics failure or bearings
or motor problems; with an almost insignificant number being weird
stuff. We did this running *thousands* of drives in racks, running a
bazzilion different access modes and patterns to see how we could make
them fail "life tests". That's not mentioning the thousands we ran
through voltage-margin tests, pressure and lack-of-pressure tests,
power-fail tests, disconnect-tests, heat and cold tests, shock tests,
and more tests you normally wouldn't imagine. The idea being that if we
could get a drive to fail, then for sure *some* customer out there would
also get the drive to crap out ... and complain bitterly when it did so.