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From: Greg Smith <gsmith@gregsmith.com>
To: Craig James <craig_james@emolecules.com>
Cc: Joshua D. Drake <jd@commandprompt.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Benchmark: Dell/Perc 6, 8 disk RAID 10
Date: Thu, 13 Mar 2008 12:01:50 -0400 (EDT)
Message-ID: <Pine.GSO.4.64.0803131151430.24943@westnet.com> (raw)
In-Reply-To: <47D9402A.3050903@emolecules.com>
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On Thu, 13 Mar 2008, Craig James wrote:

>> wal_sync_method = open_sync

There was a bug report I haven't had a chance to investigate yet that 
suggested some recent Linux versions have issues when using open_sync. 
I'd suggest popping that back to the default for now unless you have time 
to really do a long certification process that your system runs reliably 
with it turned on.

I suspect most of the improvement you saw from Joshua's recommendations 
was from raising checkpoint_segments.

> $ pgbench -c 10 -t 10000 -v test -U test
> scaling factor: 1
> number of clients: 10

A scaling factor of 1 means you are operating on a positively trivial 16MB 
database.  It also means there's exactly one entry in a table that every 
client updates on every transactions.  You have 10 clients, and they're 
all fighting over access to it.

If you actually want something that approaches useful numbers here, you 
need to at run 'pgbench -i -s 10' to get a scaling factor of 10 and a 
160MB database.  Interesting results on this class of hardware are when 
you set scaling to 100 or more (100=1.6GB database).  See 
http://www.westnet.com/~gsmith/content/postgresql/pgbench-scaling.htm for 
some examples of how that works, from a less powerful system than yours.

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



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