Re: 2.6.18-rc2, problem to wake up spinned down drive?

From: Bill Davidsen
Date: Tue Aug 08 2006 - 14:38:00 EST

Tejun Heo wrote:

Harald Dunkel wrote:

Tejun Heo wrote:

Pavel Machek wrote:

echo 1 > /sys/bus/scsi/devices/1:0:0:0/power/state

Really? I thought power/state takes 0/3 (for D0 and D3)

Yes, of course. My mistake. Sorry about the confusion. The correct
command is 'echo -n 3 > /sys/bus/scsi/devices/x:y:z:w/power/state'.

(Sure? :-)

The sleeping part is correct. That will make libata put the disk to sleep.

Now this did not work at all. The '-n 3' was probably
correct, but when I tried to access the disk, then it
did not spin up again (I waited for 5 minutes). There
was no message on the console, either.

But I could not reproduce this problem.

How do I monitor that the disk spins down and up?

But the waking up part isn't. You need to issue wake up explicitly by doing 'echo -n 0 > /sys/...' I've been a complete idiot in this thread. Please excuse me. :-(

I think the solution to your problem is adjusting command timeout to more reasonable values which should make the problem more bearable. It'll take some time to figure out how to make timeouts more intelligent without breaking support for slow devices. I'll work on that.

Tejun, would it be possible and sensible to either let the user tune this per-drive, or to have the kernel note how long {something} takes and auto-tune to that? As you said, the issue is not breaking slow devices.

bill davidsen <davidsen@xxxxxxx>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979

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