From: "Arkadiusz Miśkiewicz" <arekm@maven.pl>
To: xfs@oss.sgi.com, xfs@pzystorm.de
Cc: linux-raid@vger.kernel.org, stan@hardwarefreak.com
Subject: Re: XFS blocked task in xlog_cil_force_lsn
Date: Fri, 20 Dec 2013 23:43:47 +0100 [thread overview]
Message-ID: <201312202343.47895.arekm@maven.pl> (raw)
In-Reply-To: <52B41B67.9030308@pzystorm.de>
On Friday 20 of December 2013, Kevin Richter wrote:
> >> $ cat /sys/block/md2/md/stripe_cache_size
> >> 256
> >
> > 256 is the default and it is way too low. This is limiting your write
> > througput. Increase this to a minimum of 1024 which will give you a
> > 20MB stripe cache buffer. This should become active immediately. Add
> > it to a startup script to make it permanent.
> > $ echo 256 > /sys/block/md2/md/stripe_cache_size
> > $ time cp -a /olddisk/testfolder /6tb/foo1/
> > real 25m38.925s
> > user 0m0.595s
> > sys 1m23.182s
> >
> > $ echo 1024 > /sys/block/md2/md/stripe_cache_size
> > $ time cp -a /olddisk/testfolder /raid/foo2/
> > real 7m32.824s
> > user 0m0.438s
> > sys 1m6.759s
> >
> > $ echo 2048 > /sys/block/md2/md/stripe_cache_size
> > $ time cp -a /olddisk/testfolder /raid/foo3/
> > real 5m32.847s
> > user 0m0.418s
> > sys 1m5.671s
> >
> > $ echo 4096 > /sys/block/md2/md/stripe_cache_size
> > $ time cp -a /olddisk/testfolder /raid/foo4/
> > real 5m54.554s
> > user 0m0.437s
> > sys 1m6.268s
>
> The difference is really amazing! So 2048 seems to be the best choice.
> 60GB in 5,5minutes are 180MB/sek. That sounds a bit high, doesnt it?
> The RAID only consist of 5 SATA disks with 7200rpm.
I wonder why kernel is giving defaults that everyone repeatly recommends to
change/increase? Has anyone tried to bugreport that for stripe_cache_size
case?
--
Arkadiusz Miśkiewicz, arekm / maven.pl
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next parent reply other threads:[~2013-12-20 22:43 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <52B102FF.8040404@pzystorm.de>
[not found] ` <52B2FE9E.50307@hardwarefreak.com>
[not found] ` <52B41B67.9030308@pzystorm.de>
2013-12-20 22:43 ` Arkadiusz Miśkiewicz [this message]
2013-12-21 11:18 ` md-RAID5/6 stripe_cache_size default value vs performance vs memory footprint Stan Hoeppner
2013-12-21 12:20 ` Piergiorgio Sartor
2013-12-22 1:41 ` Stan Hoeppner
2013-12-26 8:55 ` Christoph Hellwig
2013-12-26 9:24 ` Stan Hoeppner
2013-12-26 22:14 ` NeilBrown
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