Message-ID: <4B4E14EB.7080008@2ndquadrant.com>
Date: Wed, 13 Jan 2010 13:46:03 -0500
From: Greg Smith <greg@2ndquadrant.com>
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To: Robert Haas <robertmhaas@gmail.com>
CC: Eduardo Piombino <drakorg@gmail.com>,
 pgsql-performance@postgresql.org
Subject: Re: a heavy duty operation on an "unused" table kills my
 	server
References: <e24c1d9d1001122059ic5d4721o98ccf85033b1fead@mail.gmail.com>	
	<4B4D5698.8040808@emolecules.com>	
	<e24c1d9d1001122147l1c0e2111kce25dc2c7f393087@mail.gmail.com>	
	<4B4D61DA.7080008@postnewspapers.com.au>	
	<e24c1d9d1001122303g1d4eea48h18bd73467d1fa8ec@mail.gmail.com>
	<603c8f071001130823l69804fe3m5c6fbb081c55c265@mail.gmail.com>
In-Reply-To: <603c8f071001130823l69804fe3m5c6fbb081c55c265@mail.gmail.com>
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Robert Haas wrote:
> I'm kind of surprised that there are disk I/O subsystems that are so
> bad that a single thread doing non-stop I/O can take down the whole
> server.  Is that normal?  Does it happen on non-Windows operating
> systems?  What kind of hardware should I not buy to make sure this
> doesn't happen to me?
>   
You can kill any hardware on any OS with the right abusive client.  
Create a wide table and insert a few million records into it with 
generate_series one day and watch what it does to queries trying to run 
in parallel with that.

I think the missing step here to nail down exactly what's happening on 
Eduardo's system is that he should open up some of the Windows system 
monitoring tools, look at both disk I/O and CPU usage, and then watch 
what changes when the troublesome ALTER TABLE shows up.

-- 
Greg Smith    2ndQuadrant   Baltimore, MD
PostgreSQL Training, Services and Support
greg@2ndQuadrant.com  www.2ndQuadrant.com