Re: shared_buffer - PostgreSQL 9.2

From: Keith <keith(at)keithf4(dot)com>
To: Lucas Possamai <drum(dot)lucas(at)gmail(dot)com>
Cc: pgsql-admin <pgsql-admin(at)postgresql(dot)org>
Subject: Re: shared_buffer - PostgreSQL 9.2
Date: 2016-05-13 04:29:45
Message-ID: CAHw75vskLVawEppLEnqJx=4Sp9WW7Y41WHuYbLAffj9jUH_zQA@mail.gmail.com
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On Fri, May 13, 2016 at 12:13 AM, Lucas Possamai <drum(dot)lucas(at)gmail(dot)com>
wrote:

> Hi guys,
>
> I currently have a master Postgres server with 128GB RAM.
>
> the shared_buffer is now = 51GB
>
> I read that I should decreased it to something about 32GB
>
> But, I don't wanna have IO issues, that's why the shared_buffer is too
> high.
>
> Am I going to have IO issues if decrease it?
>
> Cheers
> Lucas
>

All depends on how much of shared_buffers is in high demand. You can use
the pg_buffercache contrib module to see about how efficiently
shared_buffers is being used. Be aware that running the query against the
buffercache view can cause a slight performance hit since it briefly locks
shared_buffers to see what's there. Wrote some blog posts about how to do
this.

https://www.keithf4.com/a-large-database-does-not-mean-large-shared_buffers/
https://www.keithf4.com/a-small-database-does-not-mean-small-shared_buffers/

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