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Date:      Sun, 8 Mar 2009 13:36:09 +0100
From:      Bernd Walter <ticso@cicely7.cicely.de>
To:        "Rick C. Petty" <rick-freebsd2008@kiwi-computer.com>
Cc:        Octavian Covalschi <octavian.covalschi@gmail.com>, freebsd-hackers@freebsd.org
Subject:   Re: Spin down HDD after disk sync or before power off
Message-ID:  <20090308123608.GC82478@cicely7.cicely.de>
In-Reply-To: <20090306214738.GA50654@keira.kiwi-computer.com>
References:  <c0f49ea0903040910w496f4a72m3c3ce6882e55c307@mail.gmail.com> <200903041938.n24Jcqdr060153@lurza.secnetix.de> <20090304195614.GA179@britannica.bec.de> <20090306203057.GA49994@keira.kiwi-computer.com> <c0f49ea0903061330h3550a49l6f568ac9fa975f98@mail.gmail.com> <20090306214738.GA50654@keira.kiwi-computer.com>

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On Fri, Mar 06, 2009 at 03:47:38PM -0600, Rick C. Petty wrote:
> On Fri, Mar 06, 2009 at 03:30:14PM -0600, Octavian Covalschi wrote:
> > Why is spinning down is bad for HDD ? I believe it's better to spindown a
> > drive,
> > instead of cutting power too sudden.
> 
> Comparing those two, I'd say it shouldn't matter (although probably a
> forced spindown may be better).  But pulling power from a drive does not
> mean the drive immediately stops doing stuff.

My understanding is that without power the heads just slamm into
landing zone, while it can be done in a controlled smooth way with
power.

> I was just saying spindown on disks is bad in the first place.  Sure, you
> might save some wear and tear on the bearings, but you risk problems with
> the heads on both spindown and spinup.  In other words, if you can avoid
> power-cycling your drives, they should last longer (in that you're less
> likely to destroy the heads).

This depends on the disks.
Desktop and especially mobile drives are designed to sustain more
spin downs, but are not designed for rotating a long time.
But of course if you intend to spin up directly after spin down it
might be bad for them as well, since it isn't really saving spinning
time.
This is nothing, which should be done on reboot, but for halts it
might be reasonable to do.

-- 
B.Walter <bernd@bwct.de> http://www.bwct.de
Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.



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