Re: how delete/insert/update affects select performace?

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: <greg(at)2ndQuadrant(dot)com>,<aa(at)devshock(dot)com>, <pgsql-performance(at)postgresql(dot)org>
Subject: Re: how delete/insert/update affects select performace?
Date: 2011-09-09 12:04:35
Message-ID: 4E69BA830200002500040FD2@gw.wicourts.gov
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"Anibal David Acosta" wrote:

>> The general guidelines for Windows servers such as
>> http://wiki.postgresql.org/wiki/Tuning_Your_PostgreSQL_Server
>> recommend a fairly small setting for the shared_buffers parameters
>> on Windows--no more than 512MB.

> Even if I have a server with 16GB of ram, I must set the
> shared_buffer to 512MB on windows?
>
> In the wiki page they talk about 1/4 of ram, in my case that
> represent a shared_buffer = 4GB, that is incorrect?

There's an effective maximum, depending on the platform. On Linux
that seems to be somewhere in the 8GB to 10GB. On Windows it is much
less.

> If I can't configure more than 512MB of shared_buffer all other RAM
> is unnecessary?

The RAM not used for other purposes is used by the OS for caching.
PostgreSQL goes through that cache, so the extra memory will be used;
it's a question of what balance between PostgreSQL buffers and OS
cache gives the best performance.

-Kevin

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