Date: Mon, 7 Apr 2008 16:20:08 -0400
From: Bill Moran <wmoran@collaborativefusion.com>
To: "Hell, Robert" <Robert.Hell@fabasoft.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Looking for bottleneck during load test
Message-Id: <20080407162008.c70fbb38.wmoran@collaborativefusion.com>
In-Reply-To: 
 <B710F3299F04664DB6B37C258FDEEB94015F1CD6@FABAMAIL.fabagl.fabasoft.com>
References: 
 <B710F3299F04664DB6B37C258FDEEB94015F1BA1@FABAMAIL.fabagl.fabasoft.com>
	<ftd4ic$38k$1@ger.gmane.org>
	<B710F3299F04664DB6B37C258FDEEB94015F1CD6@FABAMAIL.fabagl.fabasoft.com>
Organization: Collaborative Fusion
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In response to "Hell, Robert" <Robert.Hell@fabasoft.com>:

> I tried different other tools for random IO (including a self written one=
 which does random lseek and read).
>=20
> This tool, started during one of our tests, achieves 2 iops (8k each).
> Started alone I get something about 1,500 iops with an avg latency of 100=
 ms.
>=20
> We are using SAN (EMC CLARiiON CX 300) - are those ~7 MB/s really our bot=
tleneck?
> Any other tuning ideas?

You know, with all the performance problems people have been bringing up
with regard to SANs, I'm putting SAN in the same category as RAID-5 ...


> -----Original Message-----
> From: pgsql-performance-owner@postgresql.org [mailto:pgsql-performance-ow=
ner@postgresql.org] On Behalf Of Ivan Voras
> Sent: Montag, 07. April 2008 14:38
> To: pgsql-performance@postgresql.org
> Subject: Re: [PERFORM] Looking for bottleneck during load test
>=20
> Hell, Robert wrote:
> > We have a PostgreSQL 8.2.7 database (~230 GB) running on a machine with=
 8 Intel Xeon Cores and 32 GB RAM (64-bit Linux 2.6.18). Data is stored on =
an EMC=B2 CLARiiON on RAID 1/0 (8 x 146 GB 15k rpm).=20
> > When we do random I/O with a small test tool (reading random 8k blocks =
from big files in 200 threads) on the disk we retrieve data with about 25 M=
B/s.
>=20
> How do you test random IO? Do you use this utility:
> http://arctic.org/~dean/randomio/ ?
>=20
> If not, try using it, with same parameters. It might be that the latency
> is destroying your performance. Do you use NFS or are you accessing the
> storage as SAN?
>=20
>=20
> --=20
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>=20
> --=20
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--=20
Bill Moran
Collaborative Fusion Inc.
http://people.collaborativefusion.com/~wmoran/

wmoran@collaborativefusion.com
Phone: 412-422-3463x4023

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