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Re: Fusion-io ioDrive

From: Greg Smith <gsmith(at)gregsmith(dot)com>
To: Jeffrey Baker <jwbaker(at)gmail(dot)com>
Cc: "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Fusion-io ioDrive
Date: 2008-07-02 01:38:04
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Lists: pgsql-performance
On Tue, 1 Jul 2008, Jeffrey Baker wrote:

> The only real problem with this benchmark is that the machine became 
> CPU-limited rather quickly. During the runs with the ioDrive, iowait was 
> pretty well zero, with user CPU being about 75% and system getting about 
> 20%.

You might try reducing the number of clients; with a single CPU like yours 
I'd expect peak throughput here would be at closer to 4 clients rather 
than 8, and possibly as low as 2.  What I normally do is run a quick scan 
of a few client loads before running a long test to figure out where the 
general area of peak throughput is.  For your 8-way box, it will be closer 
to 32 clients.

Well done test though.  When you try again with the faster system, the 
only other postgresql.conf parameter I'd suggest bumping up is 
wal_buffers; that can limit best pgbench scores a bit and it only needs a 
MB or so to make that go away.

It's also worth nothing that the gap between the two types of storage will 
go up up if you increase scale further; scale=100 is only making a 1.5GB 
or so database.  If you collected a second data point at a scale of 500 
I'd expect the standard disk results would halve by then, but I don't know 
what the fusion device would do and I'm kind of curious.  You may need to 
increase this regardless because the bigger box has more RAM, and you want 
the database to be larger than RAM to get interesting results in this type 
of test.

* Greg Smith gsmith(at)gregsmith(dot)com Baltimore, MD

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