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

To: Dennis Kaarsemaker <dennis.kaarsemaker@xxxxxxxxxxx>
Subject: Re: XFS IO multiplication problem on centos/rhel 6 using hp p420i raid controllers
From: Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx>
Date: Thu, 07 Mar 2013 07:44:51 -0600
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1362663188.16657.20.camel@seahawk>
References: <1362060736.1247.30.camel@seahawk> <20130228194023.GQ5551@dastard> <1362577992.1247.84.camel@seahawk> <20130307035737.GC6369@dastard> <1362651128.16657.13.camel@seahawk> <513891D7.4060801@xxxxxxxxxxxxxxxxx> <1362663188.16657.20.camel@seahawk>
Reply-to: stan@xxxxxxxxxxxxxxxxx
User-agent: Mozilla/5.0 (Windows NT 5.1; rv:17.0) Gecko/20130215 Thunderbird/17.0.3
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?

-- 
Stan

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