Date: Wed, 23 Oct 2013 12:14:25 -0500 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 Subject: Re: ZFS-FreeBSD + postgresql performance Message-ID: <1382548465.32073.37624113.6AA8DB42@webmail.messagingengine.com> In-Reply-To: <20131023162545.GA19794@pcjas.obspm.fr> References: <20131023162545.GA19794@pcjas.obspm.fr>
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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.
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