Summary: Re: Spin down HDD after disk sync or before power off

[RW]

On Thu, 16 Sep 2010 09:17:52 +0200
Dag-Erling Smørgrav <des at des.no> wrote:

> Garrett Cooper <gcooper at FreeBSD.org> writes:
> > Agreed. Spinning down at reboot isn't smart and seems like a good
> > way to kill a disk quicker.
> 
> *not* spinning down at halt is far worse.  Most modern disks are rated
> for hundreds of thousands of load-unload cycles, but far fewer
> emergency unloads (which is what happens when the drive loses power
> while still spinning).

As I understand it wear from spinning-down used to come from the head
actually scraping the disk surface as it lost lift, parking placed the
head on a disposable area, but modern drives take the head off the disk
altogether.

When Hitachi was specifying 300,000 unloads, they said that in testing
the drives were still working at 1,000,000, someone quoted 600,000 as
the current spec. At these levels you can be spinning the drives
down and up  ever few minutes for the normal lifetime of the drive.

Even on very old drives I doubt reboot are much of a problem, they're
rare on servers. On laptops and desktops they're rare compared to
shutdowns and suspends.