Message-Id: <1382548465.32073.37624113.6AA8DB42@webmail.messagingengine.com>
From: Mark Felder <feld@FreeBSD.org>
To: Albert Shih <Albert.Shih@obspm.fr>, pgsql-admin@postgresql.org,
 freebsd-fs@freebsd.org, freebsd-jail@freebsd.org
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Type: text/plain
In-Reply-To: <20131023162545.GA19794@pcjas.obspm.fr>
References: <20131023162545.GA19794@pcjas.obspm.fr>
Subject: Re: ZFS-FreeBSD + postgresql performance
Date: Wed, 23 Oct 2013 12:14:25 -0500
Precedence: bulk
Sender: pgsql-admin-owner@postgresql.org

On Wed, Oct 23, 2013, at 11:25, Albert Shih wrote:
> Hi
> 
> I would like to known if someone here have in production a FreeBSD server
> with postgresql and the FS for the data of postgresql is a ZFS pool. 
> 
> I'm going to buy some server with 96Go of Ram and a jbod of 12 disks (4To
> each)
> 
> The purpose is to have everything on this zfs pool (except the system who
> still on classic raid). So to have
> 
>     many jail (~20-30) running apache/mysql/etc.
>     one postgresql server with all data on the zfs.
> 
> each jail use his own zfs partition. So I can use zfs send/received to
> have
> a  mirror of everything in a other server.
> 
> My question is about the performance, I known ZFS eat all memory he can
> have (or almost), so what append when we run database like postgresql and
> jail ? (it's also the reason of 96 Go ram).
> 
> Sorry for cross-posting but it's about 3 differents things....
> 

To my understanding the solution is to change the primarycache to
"metadata" for any ZFS filesystem that you do not want ZFS to heavily
cache in memory.

Example:

# zfs set primarycache=metadata tank/usr/local/pgsql

Now for my ZFS filesystem "tank/usr/local/pgsql" where the postgres data
directory exists we will tell ZFS to only cache metadata there. Postgres
will do its own caching of the data.


-- 
Sent via pgsql-admin mailing list (pgsql-admin@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-admin