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RE: increasing ext3 or io responsiveness

Hi, all,

  I think the hdparm "-u" option is really helpful for this case.. According to the hdparm manual, it says this option will greatly increase Linux's repsonsiveness, but also brings risk of disk|file-system corruption. From my experience, the corruption risk is not too high to accept, while the responsiveness is outperformed.

 hdparm -d1 -c3 -m16 -a16 -A1 -u1 -W1 -k1 -K1 /dev/hd{a,b,c,d,...}  works great for us.


-----Original Message-----
From: Andreas Dilger [mailto:adilger clusterfs com]
Sent: Thursday, February 05, 2004 10:12 AM
To: Eric Wood
Cc: ext3-users redhat com
Subject: Re: increasing ext3 or io responsiveness

On Feb 05, 2004  12:00 -0500, Eric Wood wrote:
> Our Invoice posting routine (intensive harddrive io) freezes every few
> seconds to flush the cache.  Reading this:
> https://listman.redhat.com/archives/ext3-users/2002-November/msg00070.html
> I decided to try:
> # elvtune -r 2048 -w 131072 /dev/sda
> # echo "90 500 0 0 600000 600000 95 20 0" >/proc/sys/vm/bdflush
> # run_post_routine
> # elvtune -r 128 -w 512 /dev/sda
> # echo "30 500 0 0 500 3000 60 20 0" >/proc/sys/vm/bdflush
> # sync
> I like it, but I think that's way too lax and risky - the whole post routine
> never wrote to disk until I sync'd!  But, is there a setting that would
> ensure reliable constant i/o so that my post process is pretty much all
> flushed in real time?  Is constantly changing the bdflush parameters before
> the type of job I'm about to run a bad thing?  I noticed that changing back
> to the "30 500 0 0 500 3000 60 20 0" default doesn't flush to queue, I still
> had to "sync".

You could try deleting the journal and creating a larger one (unmounted!):

tune2fs -O ^has_journal <dev>
tune2fs -J size=128 <dev>

Max journal size is 400MB, but this can also consume that much RAM so use
with caution.

Cheers, Andreas
Andreas Dilger

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