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Re: High load and iowait but no disk access

From: Rémy Beaumont <remyb(at)medrium(dot)com>
To: josh(at)agliodbs(dot)com
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: High load and iowait but no disk access
Date: 2005-08-30 18:42:38
Message-ID: 22924e579ad7e7e0deb5133eb905618b@medrium.com (view raw or flat)
Thread:
Lists: pgsql-performance
On 30-Aug-05, at 14:32, Josh Berkus wrote:

> Remy,
>
>> The behavior we see is that when running queries that do random reads
>> on disk, IOWAIT goes over 80% and actual disk IO falls to a crawl at a
>> throughput bellow 3000kB/s (We usually average 40000 kB/s to 80000 
>> kB/s
>> on sequential read operations on the netapps)
>
> This seems pretty low for a NetApp -- you should be able to manage up 
> to
> 180mb/s, if not higher.   Are you sure it's configured correctly?
Hi Josh,

The config has been reviewed by NetApp. We do get rates higher then 
80mb/s, but on average, that's what we get.

Do you have NetApp filers deployed ?
How many spindles do you have in your volume ?
On which OS are you running Postgres ?

Thanks,

Rémy

>
> -- 
> --Josh
>
> Josh Berkus
> Aglio Database Solutions
> San Francisco
>
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