Re: Spinning down sata disk before poweroff

[David Young <dyoung%pobox.com@localhost>]

On Sat, Jun 18, 2016 at 10:51:25PM +0200, Manuel Bouyer wrote:
> On Sat, Jun 18, 2016 at 03:31:20PM -0500, David Young wrote:
> > BTW, what should we do during "manual" action, such as 'drvctl -d wd0'?
> > Seems like we should power off the drive then, too?  Otherwise, it is
> > set up for an abrupt power-loss, later.
> 
> But if you do this in order to do a rescan, you will power down/up
> the drive, which is not so good for enterprise-class drives (for drives
> designed for 24x7 SMART counts the number of stop/start cycles)

I don't understand.  Why detach in order to do a rescan?

BTW, I think that when I wrote "power off the drive," I should have
written "put it into standby."  I'm not sure the formal meaning of
standby, but I reckon it is up to the drive (controller?) whether or not
to stop the spindle as well as parking the heads.

Seen in a certain perspective, it's asymmetric that frequently the
BIOS powers a drive *up* before the bootloader runs, but the OS is
responsible to power a drive *down* during power off, or else the drive
may abruptly lose power.  Is there some way to hand responsibility for
the drive's power state back to the BIOS?  I guess that on x86, that
would be an ACPI BIOS method.  Don't we use an ACPI method to power down
the machine, after all?  ISTR we put the machine into "sleep state 5".

Dave

-- 
David Young         //\ Trestle Technology Consulting
(217) 721-9981      Urbana, IL   http://trestle.tech/