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

[Dag-Erling Smørgrav]

Alexander Best <arundel at freebsd.org> writes:
> Dag-Erling Smørgrav <des at des.no> writes:
> > No.  Where did you get that idea?  To repeat what I've said before -
> > several times - in this thread, a modern disk drive can handle hundreds
> > of thousands of controlled unloads but only a few hundred emergency
> > unloads. Given the choice between "never spin down" and "always spin
> > down", the safe alternative is "always spin down".
> atacontrol(8) says that:
>
>     "You should not set a spindown timeout on a disk with / or syslog logging
>      on it as the disk will be worn out spinning down and up all the time."
>
> this seems to indicate that spinning down a disk has quite an impact.

The problem with setting a short idle timeout is that, on a typical
laptop or desktop system, you end up spinning the disk down and back up
several hundred times a day, which increases power consumption, I/O
latency and wear.

However, a single emergency unload (what happens when the disk loses
power without first unloading the head) shortens the disk's life
expectancy as much as hundreds or thousands of controlled unloads.

Unless you think our users commonly reboot their computers hundreds or
thousands of times between each time they cycle the power, the safe
alternative is to *always* spin down during shutdown.

I truly hope this is the *last* time I have to repeat this.  It's really
not that hard to understand.

DES
-- 
Dag-Erling Smørgrav - des at des.no