From: Dave Chinner <david@fromorbit.com>
To: Michael Monnerie <michael.monnerie@is.it-management.at>
Cc: xfs@oss.sgi.com
Subject: Re: read slower than write on "mv"?
Date: Mon, 3 May 2010 21:52:07 +1000 [thread overview]
Message-ID: <20100503115207.GE2591@dastard> (raw)
In-Reply-To: <201005031054.38817@zmi.at>
On Mon, May 03, 2010 at 10:54:28AM +0200, Michael Monnerie wrote:
> This is not XFS specific, I see it on every filesys. I do a
> "mv . /newlocation" and see this with iostat:
>
> Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-
> sz avgqu-sz await svctm %util
> xvdb 608,60 2,60 25967,20 102,40 85,31 5,37
> 8,77 1,58 96,72
> xvdg 0,00 608,60 0,00 26532,10 87,19 7,55
> 12,41 0,12 7,44
>
> Reading takes 97% I/O time, writing 7%. This is on the same raidset, but
> I see the same when copying between two different single disks also. Or
> is it just an effect of write caching that writes look faster than
> reads?
Yes, just an effect of write caching hiding IO latency.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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prev parent reply other threads:[~2010-05-03 11:50 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-03 8:54 read slower than write on "mv"? Michael Monnerie
2010-05-03 11:52 ` Dave Chinner [this message]
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