Message-ID: <52B44FD8.2030105@optionshouse.com>
Date: Fri, 20 Dec 2013 08:10:32 -0600
From: Shaun Thomas <sthomas@optionshouse.com>
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To: Dave Johansen <davejohansen@gmail.com>
CC: pgsql-performance <pgsql-performance@postgresql.org>
Subject: Re: Unexpected pgbench result
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On 12/19/2013 04:06 PM, Dave Johansen wrote:

> Right now, we're running a RAID 1 for pg_clog, pg_log and pg_xlog and
> then a RAID 1+0 with 12 disks for the data. Would there be any benefit
> to running a separate RAID 1+0 with a tablespace for the indexes?

Not really. PostgreSQL doesn't currently support parallel backend 
fetches, aggregation, or really anything. It's looking like 9.4 will get 
us a lot closer to that, but right now, everything is serial.

Serial or not, separate backends will have separate read concerns, and 
PostgreSQL 9.2 and above *do* support index only scans. So 
theoretically, you might actually see some benefit there. If it were me 
and I had spindles available, I would just increase the overall size of 
the pool. It's a lot easier than managing multiple tablespaces.

-- 
Shaun Thomas
OptionsHouse | 141 W. Jackson Blvd. | Suite 500 | Chicago IL, 60604
312-676-8870
sthomas@optionshouse.com

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