Message-ID: <4890AA33.6000309@lelarge.info>
Date: Wed, 30 Jul 2008 19:51:47 +0200
From: Guillaume Lelarge <guillaume@lelarge.info>
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To: Dave North <DNorth@signiant.com>
CC: pgsql-performance@postgresql.org
Subject: Re: Database size Vs performance degradation
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Dave North a écrit :
> [...]
>> I'd suggest re-tuning as follows:
>>
>> 1) Increase shared_buffers to 10,000, test.  Things should be 
>> a bit faster.
>>
>> 2) Increase checkpoint_segments to 30, test.  What you want 
>> to watch for here whether there are periods where the server 
>> seems to freeze for a couple of seconds.  That's a 
>> "checkpoint spike".  If this happens, reduce 
>> checkpoint_segments to some sort of middle ground; some 
>> people never get above 10 before it's a problem.
>>
>> 3) Increase shared_buffers in larger chunks, as long as you 
>> don't see any problematic spikes you might usefully keep 
>> going until it's set to at least 100,000 before improvements 
>> level off.
> 
> Do you happen to know if these are "reload" or "restart" tunable
> parameters?  I think I've read somewhere before that they are restart
> parameters (assuming I've set SHMMAX high enough of course)
> 

shared_buffers and checkpoint_segments both need a restart.
> [...]
> I have to say, I've learnt a whole load from you folks here this
> morning...very enlightening.  I'm now moving on to your site Greg! :)
> 

There's much to learn from Greg's site. I was kinda impressed by all the 
good articles in it.


-- 
Guillaume.
  http://www.postgresqlfr.org
  http://dalibo.com