Subject: Re: Big Memory Boxes and pgtune
To: "Warner, Gary, Jr" <gar@uab.edu>,
 postgres performance list <pgsql-performance@postgresql.org>
References: <0cfccbc24b9e480a9452bf9ca79e96e4@UABEX4.ad.uab.edu>
From: "Joshua D. Drake" <jd@commandprompt.com>
Organization: Command Prompt, Inc.
Message-ID: <44137c5c-2117-f497-7355-12ae06c1b299@commandprompt.com>
Date: Fri, 28 Oct 2016 12:33:10 -0700
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On 10/28/2016 08:44 AM, Warner, Gary, Jr wrote:
> I've recently been blessed to move one of my databases onto a huge IBM P8 computer.   Its a power PC architecture with 20 8-way cores (so postgres SHOULD believe there are 160 cores available) and 1 TB of RAM.
>
> I've always done my postgres tuning with a copy of "pgtune" which says in the output:
>
> # WARNING
> # this tool not being optimal
> # for very high memory systems
>
> So . . . what would I want to do differently based on the fact that I have a "very high memory system"?

The most obvious is that you are going to want to have (depending on 
PostgreSQL version):

* A very high shared_buffers (in newer releases, it is not uncommon to 
have many, many GB of)
* Use that work_mem baby. You have 1TB available? Take your average data 
set return, and make work_mem at least that.
* IIRC (and this may be old advice), maintenance_work_mem up to 4GB. As 
I recall it won't effectively use more than that but I could be wrong.

Lastly but most importantly, test test test.

JD

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