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Date:      Tue, 01 Apr 2003 09:19:50 -0500
From:      Jason Andresen <jandrese@mitre.org>
To:        Craig Boston <craig@meoqu.gank.org>
Cc:        FreeBSD Stable List <freebsd-stable@freebsd.org>
Subject:   Re: vinum performance
Message-ID:  <3E89A006.7020301@mitre.org>
In-Reply-To: <1049147744.98637.57.camel@owen1492.uf.corelab.com>
References:  <20030330125138.K23911@leelou.in.tern>	 <3E870CC7.5000204@mac.com> <20030330175605.E23911@leelou.in.tern>	 <3E87204C.5060304@ludd.luth.se> <3E88524A.1060600@mitre.org>	 <3E88AECD.10607@liwing.de> <3E88B601.90802@mitre.org> <1049147744.98637.57.camel@owen1492.uf.corelab.com>

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Craig Boston wrote:
> On Mon, 2003-03-31 at 15:41, Jason Andresen wrote:
> 
>>(Both of these were on previously untouched files to prevent any 
>>caching, and the "write" test is on a new file, not rewriting an old one)
>>Write speed:
>>81920000 bytes transferred in 3.761307 secs (21779663 bytes/sec)
>>Read speed:
>>81920000 bytes transferred in 3.488978 secs (23479655 bytes/sec)
>>
>>But on the RAID5:
>>Write speed:
>>81920000 bytes transferred in 17.651300 secs (4641018 bytes/sec)
>>Read speed:
>>81920000 bytes transferred in 4.304083 secs (19033090 bytes/sec)
> 
> 
> Disclaimer: IANAVE (I am not a Vinum Expert)
> 
> What block size are you using with dd?  If your bs= is less than your
> RAID stripe size, it seems like it would end up doing unnecessary
> read-modify-write cycles...

Commands used:

dd if=/dev/zero of=test bs=8192 count=1000

and

dd if=random_unused_file_larger_than_80MB of=/dev/null bs=8192 \ count=10000

My stripe size is 384k.

-- 
   \  |_ _|__ __|_ \ __| Jason Andresen        jandrese@mitre.org
  |\/ |  |    |    / _|  Network and Distributed Systems Engineer
_|  _|___|  _| _|_\___| Office: 703-883-7755




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