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Date: Tue, 07 Aug 2007 22:26:46 -0600 From: Robert Hancock <hancockr@...w.ca> To: Henrique de Moraes Holschuh <hmh@....eng.br> Cc: Tejun Heo <htejun@...il.com>, Michael Sedkowski <sedmich@...il.com>, "Rafael J. Wysocki" <rjw@...k.pl>, linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org, linux-acpi@...r.kernel.org Subject: Re: Disk spin down issue on shut down/suspend to disk 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 To email, remove "nospam" from hancockr@...pamshaw.ca Home Page: http://www.roberthancock.com/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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