Henrique de Moraes Holschuh wrote:
On Tue, 07 Aug 2007, Robert Hancock wrote:
You *do* have to worry about it in any box you turn off daily. Desktop
HDs will croak fast in that scenario, laptop HDs less so, but still too
fast. A very good laptop HD can last about 20k emergency unloads (this
is a unit that can do about 600k normal unloads in its lifetime).
Desktop and server HDs don't even come close to those numbers, last time
I checked.
It only matters on hard drives which actually use load-unload heads. Lots
of desktop/server drives (perhaps some laptop ones as well) still use
contact start/stop, which doesn't remove the heads from the platters on
I am not so sure about that.
Please correct me if I am wrong, but contact stop in an emergency retract
shakes the head assembly badly as well. It subjects the head assembly to
higher acceleration than a normal seek, and a nasty impulse at impact with
the stopper. And I very much doubt it is nice to the heads to slide into
the parking zone at high speed and hit the bumper while over it.
Unless I missed something, I don't why an emergency retract would not be as
big a problem as an emergency unload.
Maybe we should hunt down some proper datasheets for drives lacking head
load/unload technology, and check what they say about emergency unloads...
I did a bit of a look and didn't find any mention of the subject for
drives using contact start/stop. I did find mention that the unload
torque needed is quite a bit higher on load/unload systems, so I would
imagine that having to extract or store that energy for emergency
unloads would be more of a demanding task and might be a rougher process.
Just judging from the sound, though, hard power-offs on a desktop
Seagate Barracuda 7200.10, for example, which is contact start/stop,
don't really sound any different from a commanded standby. On the laptop
drives I've seen you can really tell the difference.
--
Robert Hancock Saskatoon, SK, Canada
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Home Page: http://www.roberthancock.com/
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