Re: Software RAID (non-preempt) server blocking question. (2.6.20.4)

[Justin Piszcz]

On Thu, 29 Mar 2007, Neil Brown wrote:

> On Tuesday March 27, jpiszcz@xxxxxxxxxxxxxxx wrote:
> > I ran a check on my SW RAID devices this morning.  However, when I did so,
> > I had a few lftp sessions open pulling files.  After I executed the check,
> > the lftp processes entered 'D' state and I could do 'nothing' in the
> > process until the check finished.  Is this normal?  Should a check block
> > all I/O to the device and put the processes writing to a particular device
> > in 'D' state until it is finished?
>
> No, that shouldn't happen.  The 'check' should notice any other disk
> activity and slow down if anything else is happening on the device.
>
> Did the check run to completion?  And if so, did the 'lftp' start
> working normally again?
Yes it did and the lftp did start working normally again.

> Did you look at "cat /proc/mdstat" ?? What sort of speed was the check
> running at?
Around 44MB/s.

I do use the following optimization, perhaps a bad idea if I want other 
processes to 'stay alive'?

echo "Setting minimum resync speed to 200MB/s..."
echo "This improves the resync speed from 2.1MB/s to 44MB/s"
echo 200000 > /sys/block/md0/md/sync_speed_min
echo 200000 > /sys/block/md1/md/sync_speed_min
echo 200000 > /sys/block/md2/md/sync_speed_min
echo 200000 > /sys/block/md3/md/sync_speed_min
echo 200000 > /sys/block/md4/md/sync_speed_min



> NeilBrown
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