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From: David Boreham <david_list@boreham.org>
Cc: pgsql-performance@postgresql.org
Subject: Re: performance on new linux box
Date: Thu, 08 Jul 2010 15:43:13 -0600
Message-ID: <4C364671.7010109@boreham.org> (raw)
In-Reply-To: <B9A709F368FAAF4DB4B33870F72A141D0106C0E8@CORPUSMX30A.corp.emc.com>
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	<95971335.20100708211351@erwied.eu>
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	<4C35E4CA020000250003327E@gw.wicourts.gov>
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	<4C363CAE.7010401@emolecules.com>
	<B9A709F368FAAF4DB4B33870F72A141D0106C0E8@CORPUSMX30A.corp.emc.com>

On 7/8/2010 3:18 PM, Timothy.Noonan@emc.com wrote:
> How does the linux machine know that there is a BBU installed and to
> change its behavior or change the behavior of Postgres? I am
> experiencing performance issues, not with searching but more with IO.
>    
It doesn't change its behavior at all. It's in the business of writing 
stuff to a file and waiting until that stuff has been put on the disk 
(it wants a durable write). What the write buffer/cache does is to 
inform the OS, and hence PG, that the write has been done when in fact 
it hasn't (yet). So the change in behavior is only to the extent that 
the application doesn't spend as much time waiting.





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