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Re: XFS IO multiplication problem on centos/rhel 6 using hp p420i raid c

To: stan@xxxxxxxxxxxxxxxxx
Subject: Re: XFS IO multiplication problem on centos/rhel 6 using hp p420i raid controllers
From: Dennis Kaarsemaker <dennis.kaarsemaker@xxxxxxxxxxx>
Date: Thu, 07 Mar 2013 14:52:56 +0100
Cc: xfs@xxxxxxxxxxx
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On Thu, 2013-03-07 at 07:44 -0600, Stan Hoeppner wrote:
> On 3/7/2013 7:33 AM, Dennis Kaarsemaker wrote:
> > The "ten times as many bytes" is constant, so it is constantly writing
> > ten times as much data.
> Where in the IO stack are you counting the bytes?  Are 10x as many bytes
> actually hitting the AGs?  I.e. are you consuming 10x more (real--not
> counting preallocation) space in the filesystem?  Or are you simply
> seeing larger IOs in flight per unit time, but the same total amount of
> IO bytes?

I'm counting them with vmstat, iostat and collectl as can be seen in the
various outputs I've sent. I hope that answers your question as I have
no idea how to see what's hitting the AG's.

I am not using ten times as much space, as that wouldn't fit on the
Dennis Kaarsemaker, Systems Architect
Herengracht 597, 1017 CE Amsterdam
Tel external +31 (0) 20 715 3409
Tel internal (7207) 3409

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