Date: Fri, 6 Mar 2009 15:30:14 -0600 From: Octavian Covalschi <octavian.covalschi@gmail.com> To: rick-freebsd2008@kiwi-computer.com Cc: freebsd-hackers@freebsd.org Subject: Re: Spin down HDD after disk sync or before power off Message-ID: <c0f49ea0903061330h3550a49l6f568ac9fa975f98@mail.gmail.com> In-Reply-To: <20090306203057.GA49994@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>
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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@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 > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org" >
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