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SubjectRe: 2.6.18-rc2, problem to wake up spinned down drive?
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@tmr.com>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979

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