[ltp] [PATCH] 2.6.17: Unload disks heads before powering down

[Henrique de Moraes Holschuh]

On Fri, 22 Sep 2006, Shem Multinymous wrote:
> On 9/22/06, Henrique de Moraes Holschuh <hmh@hmh.eng.br> wrote:
> >The attached patch applies to 2.6.17.  It won't work with > They command 
> >the HDs to unload heads before the system is shutdown (hint:
> >most BIOSes, including the ThinkPads, will NOT do it for you).
> 
> Is this needed?! I'm pretty sure all modern (i.e., recent decade)
> drives do it themselves, using the energy left in the spindle.

What you describe IS an emergency unload, and it is exactly what the patch
wants to prevent.  Your disk will not power down with the heads loaded, it
WILL unload them one way or the other.  And if you want the disk to last
longer, you want it done the nice way and not through the emergency unload
system.

Normal unloads are controlled, and do a lot less damage (as in "normal
wear") to the head assembly and arms.  Hitachi is very explicit that
emergency unloads are 100 times more stressful to their hardware than
regular unloads, for example.  Given that you can actually *hear* the
difference quite easily between the two unloads...

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh