Re: IBM HDAPS things are looking up (was: Re: [Hdaps-devel] Re: [ltp] IBM HDAPS Someone interested? (Accelerometer))

[Jens Axboe]

On Mon, Jul 04 2005, Arjan van de Ven wrote:
> 
> > > This is exactly what I said. Use hdparm to make the HD park 
> > > inmediatelly. I did send the email to the HDPARM developer, but he never 
> > > replied. I asked him what would be the best way to make the HD park with 
> > > no exception and then let it come back 5 or 10 seconds later.
> > 
> > IIRC, you don't have to do anything to wake up the drive after a
> > STANDBYNOW command, if you want to be on the safe side you just issue an
> > IDLEIMMEDIATE. So your code will look something like:
> 
> the problem for this will be that this app will also want to prevent ANY
> io going to the disk for a few seconds.
> 
> I mean, what use is parking the head if you notice the laptop falling,
> when the kernel submits IO to it and wakes it up again before it hits
> the ground :)

Yeah, that likely needs a little help from the ide driver. If you force
a spindown, you will effectively have parked the head for as long as the
spindown + spinup takes. That could turn out to be enough, it will take
more than 1-2 seconds anyways.

-- 
Jens Axboe

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