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List:       debian-user
Subject:    Re: file systems
From:       Stan Hoeppner <stan () hardwarefreak ! com>
Date:       2011-05-05 9:38:16
Message-ID: 4DC27008.2080105 () hardwarefreak ! com
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On 5/2/2011 5:54 PM, Boyd Stephen Smith Jr. wrote:

> I'm slightly surprised by the results.  It's possible it was slightly weighted
> toward JFS because of the "%CPU" and "Ops/%CPU" metrics, which I don't think
> matter too much.

As I mentioned previously, the only relevant graph of each set is the 
one at the top of each page, either MB/s or IOPS.  The other graphs are 
useless for any kind of ranking, and in fact will likely produce 
misleading rankings.  If your ranking program is looking at tall bars, 
it will make an inverse ranking error WRT %CPU data, where the lower 
bars are better.  %CPU isn't relevant anyway as any 4+ core server 
shipped in the past 3 years has a huge excess of CPU/mem bandwidth in 
relation to IO.

If you rank strictly based on the first graph of each test result page 
you'll see why I use the word "trounces".

> I'd love to see data for 2.6.32 (Squeeze) and 2.6.38 (Wheezy/Sid).

XFS had horrible metadata performance until 2.6.35 which introduced 
delayed logging, so the mail server test will have much lower results 
with the stock Squeeze kernel.  There was an additional XFS patch in 
2.6.39 which speeds metadata operations up even further.  From 2.6.35 to 
2.6.38 you won't see much, if any, difference in XFS performance.  I 
don't keep up with the other filesystems so I can't comment on their 
development.

-- 
Stan


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