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Re: SAN performance mystery

From: Tim Allen <tim(at)proximity(dot)com(dot)au>
To: Jeff Trout <threshar(at)torgo(dot)978(dot)org>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: SAN performance mystery
Date: 2006-06-19 06:12:07
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
Jeff Trout wrote:
> On Jun 16, 2006, at 5:11 AM, Tim Allen wrote:
>> One curious thing is that some postgres backends seem to spend an  
>> inordinate amount of time in uninterruptible iowait state. I found  a 
>> posting to this list from December 2004 from someone who reported  
>> that very same thing. For example, bringing down postgres on the  
>> customer box requires kill -9, because there are invariably one or  
>> two processes so deeply uninterruptible as to not respond to a  
>> politer signal. That indicates something not quite right, doesn't it?
> Sounds like there could be a driver/array/kernel bug there that is  
> kicking the performance down the tube.
> If it was PG's fault it wouldn't be stuck uninterruptable.

That's what I thought. I've advised the customer to upgrade their kernel 
drivers, and to preferably upgrade their kernel as well. We'll see if 
they accept the advice :-|.


Tim Allen          tim(at)proximity(dot)com(dot)au
Proximity Pty Ltd

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