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Re: sunit not working

To: salmr0@xxxxxx
Subject: Re: sunit not working
From: Nathan Scott <nscott@xxxxxxxxxx>
Date: Wed, 13 Jun 2007 09:21:18 +1000
Cc: "Salmon, Rene" <Rene.Salmon@xxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <902286657-1181653953-cardhu_decombobulator_blackberry.rim.net-1527539029-@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
Organization: Aconex
References: <1181606134.7873.72.camel@holwrs01> <1181608444.3758.73.camel@xxxxxxxxxxxxxx> <902286657-1181653953-cardhu_decombobulator_blackberry.rim.net-1527539029-@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
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On Tue, 2007-06-12 at 13:12 +0000, salmr0@xxxxxx wrote:
> 
> 
> 
> 
> 
> Thanks that helps.  Now that I know I have the right sunit and swidth
> I have a performace related question.
> 
> If I do a dd on the raw device or to the lun directy I get speeds of
> around 190-200 MBytes/sec.
> 
> As soon as I add xfs on top of the lun my speeds go to around 150
> MBytes/sec. This is for a single stream write using various block
> sizes on a 2 Gbit/sec fiber channel card.
> 

Reads or writes?
What are your I/O sizes?
Buffered or direct IO?
Including fsync time in there or not?  etc, etc.

(Actual dd commands used and their output results would be best)
xfs_io is pretty good for this kind of analysis, as it gives very
fine grained control of operations performed, has integrated bmap
command, etc - use the -F flag for the raw device comparisons).

> Is this overhead more or less what you would expect from xfs? Or is
> there some tunning I need to do? 

You should be able to get very close to raw device speeds esp. for a
single stream reader/writer, with some tuning.

cheers.


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