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Re: Benchmarking results, questions

From: Brian Ghidinelli <brian(at)pukkasoft(dot)com>
To: sfpug(at)postgresql(dot)org
Subject: Re: Benchmarking results, questions
Date: 2006-01-17 19:12:31
Message-ID: (view raw, whole thread or download thread mbox)
Lists: sfpug
Josh, thanks for your response and insight.  At the moment, my database 
is trivially small (dump size of ~40M, grows by a few hundred k a day 
but that will speed up as usage keeps increasing).  Most of this is to 
better understand PG and filesystems.  A couple of short follow-ups:

Josh Berkus wrote:
> I'd follow up with a more "realistic" test such as DBT2 or Jan-TPCW.

I'll take a look into these.  I'm also looking at generating a long 
transaction list from my existing application and playing those back to 
see what the performance is like with some realistic queries.

>> * These are all with a default postgresql.conf. My plan was to test it
>> out of the box to determine filesystem/array setup first and then tune
> You're potentially masking some underlying issues.

Is work mem the most critical of these or what else should I look at? 
With a small DB like I currently have, I expect performance whould 
skyrocket once available memory > database size.  Are there any other 
tricks related to putting the whole DB into memory?

> Maybe ... depends on the server.   In practice, I've found that 95% of OS 
> files get cache semi-permanently in RAM and there's very little disk 
> activity associated with the OS files.   As a result, putting the XLog on 
> the disk with the OS files works fine.

I'll try a 4-disk RAID 10 with the log on the OS partition and see how 
that works next.  Since the pgbench doesn't do a lot of realistic 
writing though, I expect I'll see a minor increase?

> Hey, there is no such thing as enough testing so your study is very 
> welcome.

When I finish, I will post my spreadsheet for reference.  Thanks,


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Subject: Followup on benchmarks, results
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Subject: Re: Benchmarking results, questions

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