From: Mark Kirkwood <markir@paradise.net.nz>
To: pgsql-performance@postgresql.org
Cc: tim@proximity.com.au
Cc: mstone+postgres@mathom.us
Subject: Re: SAN performance mystery
Date: Tue, 20 Jun 2006 11:16:35 +1200
Message-ID: <44973053.4080906@paradise.net.nz> (raw)
In-Reply-To: <20060619102430.GD3303@mathom.us>
References: <4491D61B.9040507@proximity.com.au>
<1150408614.26538.95.camel@state.g2switchworks.com>
<449677EB.50609@proximity.com.au>
<20060619102430.GD3303@mathom.us>
Michael Stone wrote:
> On Mon, Jun 19, 2006 at 08:09:47PM +1000, Tim Allen wrote:
>> Certainly, the read performance of the SATA disk still beats the SAN,
>> and there is no way to lie about read performance.
>
> Sure there is: you have the data cached in system RAM. I find it real
> hard to believe that you can sustain 161MB/s off a single SATA disk.
>
Agreed - approx 60-70Mb/s seems to be the ballpark for modern SATA
drives, so get get 161Mb/s you would need about 3 of them striped
together (or a partially cached file as indicated).
What is interesting is that (presumably) the same test is getting such
uninspiring results on the SAN...
Having said that, I've been there too, about 4 years ago with a SAN that
had several 6 disk RAID5 arrays, and the best sequential *read*
performance we ever saw from them was about 50Mb/s. I recall trying to
get performance data from the vendor - only to be told that if we were
doing benchmarks - could they have our results when we were finished!
regards
Mark
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To: pgsql-performance@postgresql.org
Cc: markir@paradise.net.nz, tim@proximity.com.au, mstone+postgres@mathom.us
Subject: Re: SAN performance mystery
In-Reply-To: <44973053.4080906@paradise.net.nz>
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