Spin down HDD after disk sync or before power off

[Octavian Covalschi]

Why is spinning down is bad for HDD ? I believe it's better to spindown a
drive,
instead of cutting power too sudden.

On Fri, Mar 6, 2009 at 2:30 PM, Rick C. Petty <
rick-freebsd2008 at kiwi-computer.com> wrote:

> On Wed, Mar 04, 2009 at 08:56:14PM +0100, Joerg Sonnenberger wrote:
> > 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.
>
> I believe you are incorrect.  Most hard drives do an "autopark" of the head
> into the landing zone (which is near the spindle) when power is lost.  My
> understanding is that because it is spinning so fast, the heads can fly for
> quite a long time so the HDD has enough time to autopark and such an
> operation does not consume much power.  Thus the operation can be performed
> with a little capacitance or by using some of the mechanical energy in the
> spindle.
>
> If drives did not auto, there would be orders of magnitude more failures
> due to head crashes.  The heads absolutely have to be retracted into the
> landing zone if the spindle speed is too low or the drive will fail.
>
> What's actually bad for the drives is the actual spinup and spindowns,
> which require the head to sit in the very bumpy landing zone until the
> drive reaches optimal spindle speed and thus enough airflow to safely move
> the heads around the platter without contact.
>
> Strangely, atacontrol(8) has a command for spindown (which is inherently
> bad for drives yet still a reasonable feature) but there is no command for
> spinup.  I wish there was a spinup command because I've seen drives that
> won't do a spinup until they receive a special ATA command.  I was never
> able to find any docs, so if anyone knows the command I'd be willing to
> write a patch against atacontrol!
>
> -- Rick C. Petty
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