Re: Looking for bottleneck during load test

I tried different other tools for random IO (including a self written one which does random lseek and read).

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.

We are using SAN (EMC CLARiiON CX 300) - are those ~7 MB/s really our bottleneck?
Any other tuning ideas?

Regards,
Robert

-----Original Message-----
From: pgsql-performance-owner(at)postgresql(dot)org [mailto:pgsql-performance-owner(at)postgresql(dot)org] On Behalf Of Ivan Voras
Sent: Montag, 07. April 2008 14:38
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: [PERFORM] Looking for bottleneck during load test

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 EMC² CLARiiON on RAID 1/0 (8 x 146 GB 15k rpm).
> 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 MB/s.

How do you test random IO? Do you use this utility:
http://arctic.org/~dean/randomio/ ?

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?

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