From owner-freebsd-hackers@FreeBSD.ORG  Wed Mar  4 20:15:51 2009
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Date: Wed, 4 Mar 2009 20:56:14 +0100
From: Joerg Sonnenberger <joerg@britannica.bec.de>
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Subject: Re: Spin down HDD after disk sync or before power off
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On Wed, Mar 04, 2009 at 08:38:52PM +0100, Oliver Fromme wrote:
> Octavian Covalschi wrote:
>  > I'm looking a way to spin down HDD just right before power off. Why?
>  > 
>  > Because currently when I call "shutdown -p now", HDD is powered off at it's
>  > full speed (7200.4) and as a result
>  > I hear a noise of stopping/spinning down of HDD, and _this_ concerns me as
>  > I'm afraid it can damage HDD.
> 
> You don't have to spin down a disk before powering it off.
> The noise you hear is probably caused by the "autopark"
> feature of the drive.  It is harmless.

This is not true. Many hard disks don't like having to do an emergency
shutdown as it affects the disk life time negatively. That's what
happens if you poweroff the machine when the disks are still spinning.

Joerg