Re: Looking for bottleneck during load test

In response to "Hell, Robert" <Robert(dot)Hell(at)fabasoft(dot)com>:

> 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?

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(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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--
Bill Moran
Collaborative Fusion Inc.
http://people.collaborativefusion.com/~wmoran/

wmoran(at)collaborativefusion(dot)com
Phone: 412-422-3463x4023

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