hard disk power down

[David Zeuthen]

Hi,

Sorry for the lag - been traveling,

On Mon, 2007-05-14 at 13:18 +0100, Richard Hughes wrote:
> On Mon, 2007-05-14 at 12:56 +0100, Andy Green wrote:
> > 
> > If in reality you expected the drive to last 5 years and it was in use
> > half that time, spreading the budget of 300,000 starts and stops over
> > that period looks like you can afford to do something like 6 an
> > hour...
> > vs one an hour for the 3.5" drive...
> 
> Cheers for doing that - that's useful to know. David, this makes some of
> the discussion with DannyK moot - what do you think about hdd powerdown
> from the desktop?

Hmm, I think this just needs to happen automagically when g-p-m calls
SetPowerSave() on HAL

http://people.freedesktop.org/~david/hal-spec/hal-spec.html#interface-device-systempower

e.g. you'd have the option in g-p-m for both the "On AC" and "On
battery" tabs saying

 [x] When idle, power down hard disks and peripherals

that defaults to [x] for "On battery" and [ ] for "On AC". So as far as
I'm concerned the magic just happens in pm-powersave (which is what
SetPowerSave() on HAL calls). 

(I also think it's preferable to avoid using hdparm or sdparm for this;
the kernel driver for the hard drive / controller needs to export a
power mgmt aware interface that we can easily poke using sysfs.)

The key thing here is this: The desktop user only needs to tweak a
simple setting (that's all what users care about; "save power or not"),
and we can expand the mechanism of what this does in pm-powersave.

How about that?

      David