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Re: Performance considerations for very heavy INSERT traffic

From: Vivek Khera <vivek(at)khera(dot)org>
To: Postgresql Performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Performance considerations for very heavy INSERT traffic
Date: 2005-09-21 15:57:42
Message-ID: 241EAFA1-B76D-46C1-9536-69B3B05AA64C@khera.org (view raw or flat)
Thread:
Lists: pgsql-performance
On Sep 12, 2005, at 6:02 PM, Brandon Black wrote:

>         - splitting the xlog and the data on distinct physical  
> drives or arrays
>
> That would almost definitely help, I haven't tried it yet.   
> Speaking of the xlog, anyone know anything specific about the WAL  
> tuning parameters for heavy concurrent write traffic?  What little  
> I could dig up on WAL tuning was contradictory, and testing some  
> random changes to the parameters hasn't been very conclusive yet.   
> I would imagine the WAL buffers stuff could potentially have a  
> large effect for us.
>

you will want to make your pg_xlog RAID volume BIG, and then tell  
postgres to use that space: bump up checkpoint_segments (and suitably  
the checkpoint timeouts).  I run with 256 segments and a timeout of 5  
minutes.  The timeout refletcs your  expected crash recovery time, so  
adjust it wisely....

Also, you should consider how you split your drives across your RAID  
data channels on your test machine: I put each pair of the RAID10  
mirrors on opposite channels, so both channels of my RAID controller  
are pretty evenly loaded during write.

Vivek Khera, Ph.D.
+1-301-869-4449 x806


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