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read slower than write on "mv"?

To: xfs@xxxxxxxxxxx
Subject: read slower than write on "mv"?
From: Michael Monnerie <michael.monnerie@xxxxxxxxxxxxxxxxxxx>
Date: Mon, 3 May 2010 10:54:28 +0200
Organization: it-management http://it-management.at
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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 

mit freundlichen Grüssen,
Michael Monnerie, Ing. BSc

it-management Internet Services
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