linux-kernel - Re: power off disk drives while running

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Message-ID: <b2d05de20708181221t63eea603v43973edc53a5c5e0@mail.gmail.com>
Date:	Sat, 18 Aug 2007 11:21:02 -0800
From:	"Brennan Ashton" <comphappy@...il.com>
To:	"Jan Engelhardt" <jengelh@...putergmbh.de>
Cc:	"Marty Leisner" <leisner@...hester.rr.com>,
	linux-kernel@...r.kernel.org
Subject: Re: power off disk drives while running

On 8/18/07, Jan Engelhardt <jengelh@...putergmbh.de> wrote:
>
> On Aug 18 2007 12:08, Marty Leisner wrote:
> >
> >In embedded system design, it may be useful to poweroff the disks (as opposed
> >to merely spinning them down).  We want to leave the system running while
> >the disk is powered down, and let the disk powerup when it needs to be
> >spun up.
>
> That means you also have to power it on...
>
> >While the "power off mechanism" would be platform dependent, is there a
> >generic path to announce "prepare for power going away"?
>
> I do not see why that would be needed from a software point of view. Just make
> sure that the disk does not needlessy emergency-park when pulling power. When
> someone wants to write to disk, the request goes to the device driver, which
> hands it to the controller, which hands it to the disk. And your controller
> should be able to handle it (e.g. wait until reconnect) when there is a request
> for a disk that is powered off.
>
>
>         Jan
> --
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I see this a a very important feature in the embedded system relm, I
have worked on two projects that required extreme power management,
and massive data storage.  The ability to fully turn off a drive while
the system is running is key. It seems like this should be able to be
done from a kernel point of view rather than extra hardware. Although
if is not in the IDE/SATA spec then extra hardware would be necessary.
-- 
Brennan Ashton
Bellingham, Washington

"The box said, 'Requires Windows 98 or better'. So I installed Linux"
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