From: Janning Vygen <vygen@kicktipp.de>
To: pgsql-performance@postgresql.org
Subject: Re: Write performance
Date: Thu, 24 Jun 2010 15:45:31 +0200
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On Thursday 24 June 2010 15:16:05 Janning wrote:
> On Thursday 24 June 2010 14:53:57 Matthew Wakeling wrote:
> > On Thu, 24 Jun 2010, Janning wrote:
> > > We have a 12 GB RAM machine with intel i7-975 and using
> > > 3 disks "Seagate Barracuda 7200.11, ST31500341AS (1.5 TB)"
> > >
> > For each drive, you will be able to read/write approximately 8kB /
> > 0.0085s, giving 941kB per second. If you have multiple processes all
> > doing random access, then you may be able to utilise both discs and get
> > double that.
>
> So with your calculation I have a maximum of 2MB/s random access. So i
> really need to upgrade my disk configuration!

i was looking at tomshardware.com and the fastest disk is

   Maxtor Atlas 15K II * 8K147S0,SAS,147 GB, 16 MB Cache,15000 rpm

with 5.5 ms random access time. 

So even if i switch to those disks i can only reach a perfomace gain of 1.5, 
right? 

To achieve a better disk performance by factor of ten, i need a raid-10 setup 
with 12 disks (so i have 6 raid-1 bundles). Or are there other factors with 
high end disks? 

kind regards 
Janning