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From: Greg Smith <gsmith@gregsmith.com>
To: Craig James <craig_james@emolecules.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: RAID 10 Benchmark with different I/O schedulers (was: Performance increase with elevator=deadline)
Date: Mon, 5 May 2008 23:59:30 -0400 (EDT)
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In-Reply-To: <481F992D.7070509@emolecules.com>
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On Mon, 5 May 2008, Craig James wrote:

> pgbench -i -s 20 -U test

That's way too low to expect you'll see a difference in I/O schedulers. 
A scale of 20 is giving you a 320MB database, you can fit the whole thing 
in RAM and almost all of it on your controller cache.  What's there to 
schedule?  You're just moving between buffers that are generally large 
enough to hold most of what they need.

> pgbench -c 10 -t 50000 -v -U test

This is OK, because when you increase the size you're not going to be 
pushing 3500 TPS anymore and this test will take quite a while.

--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD

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  Subject: Re: RAID 10 Benchmark with different I/O schedulers (was: Performance increase with elevator=deadline)
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