Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.80) (envelope-from ) id 1VlJPe-00063I-Mg for pgsql-performance@arkaria.postgresql.org; Tue, 26 Nov 2013 14:14:50 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.80) (envelope-from ) id 1VlJPd-0004Fj-V7 for pgsql-performance@arkaria.postgresql.org; Tue, 26 Nov 2013 14:14:50 +0000 Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29]) by malur.postgresql.org with esmtp (Exim 4.80) (envelope-from ) id 1VlJPb-0004Fa-PI for pgsql-performance@postgresql.org; Tue, 26 Nov 2013 14:14:47 +0000 Received: from tamriel.snowman.net ([2001:4830:167b::11]) by magus.postgresql.org with esmtp (Exim 4.80) (envelope-from ) id 1VlJPT-0000CJ-TR for pgsql-performance@postgresql.org; Tue, 26 Nov 2013 14:14:46 +0000 Received: by tamriel.snowman.net (Postfix, from userid 1000) id B7B1B5F7DA; Tue, 26 Nov 2013 09:19:44 -0500 (EST) Date: Tue, 26 Nov 2013 09:19:44 -0500 From: Stephen Frost To: Boszormenyi Zoltan Cc: Heikki Linnakangas , Lee Nguyen , pgsql-performance@postgresql.org Subject: Re: Postgresql in a Virtual Machine Message-ID: <20131126141944.GO17272@tamriel.snowman.net> References: <5293B0B9.1060200@vmware.com> <5294A77F.8050508@cybertec.at> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="LQQvF5v7Jh3duU4E" Content-Disposition: inline In-Reply-To: <5294A77F.8050508@cybertec.at> X-Editor: Vim http://www.vim.org/ X-Info: http://www.snowman.net X-Operating-System: Linux/3.8.0-25-generic (x86_64) X-Uptime: 09:16:18 up 136 days, 10:25, 11 users, load average: 0.09, 0.06, 0.05 User-Agent: Mutt/1.5.21 (2010-09-15) X-Pg-Spam-Score: -1.9 (-) List-Archive: List-Help: List-ID: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: X-Mailing-List: pgsql-performance Precedence: bulk Sender: pgsql-performance-owner@postgresql.org --LQQvF5v7Jh3duU4E Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Zoltan, * Boszormenyi Zoltan (zb@cybertec.at) wrote: > When the virtual disk is a disk file on the host machine, we've measured > 20% or lower. The host used Fedora 19/x86_64 with IIRC a 3.10.x Linux kernel > with EXT4 filesystem (this latter is sure, not IIRC). The effect was observed > both under Qemu/KVM and Xen. Interesting- that's far worse than I would have expected. Was this test done with paravirtualized drivers? If not, I can certainly understand the terrible performance. Independently of that, I'll add my own 2c that DB people tend to be pretty paranoid and the current round of VM technologies out there have caused more than one person to lose data because fsync wasn't honored all the way down to the disk. This is especially true of 'home-grown' setups, imv, but I'm sure you could configure the commercial offerings to lie to the guest OS too. Of course, there are similar concerns about a SAN or even local RAID cards, but there's a lot more general familiarity and history around those which reduces the risk there (or at least, that's the thought). Thanks, Stephen --LQQvF5v7Jh3duU4E Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJSlK4AAAoJEO1sijiDR2RV+q4P/0rxml8vAiIEPStTpaqaHoMk qNOSxky/7Dp/F9Ji/psEUSgGBjFMYmZutPjps1uTOH6BWOGddpcgQYi/huTAflRw 1NWaINGv0psRrSW99PPS1WbFFN0YbxBRAD66VgxJYVgc8l3XXD+qXFta280oFOHT ETTG8ZpSmryx8qFYZ0WYnS5xljwJ78PNo2nKKNENpvz07vlJeXJYxw5CP7hVqcyE dW7RqSaxb5wXsv+1E297fS/F0/qSbdPzP9tYxMo4cx6GM9qGRYtdYrJ6y85SycG5 LhfDVcJt+rYjHup+eNpxFYxgWWidH/uC1ub0XBHpX5ws1Z8nAew+/xrRdwDQHKIN avhXqxffh/rO5WH5DRs4YirxL+rhosr/UonoJ/3MiETQlOx/Kpr4MymStDrKUvRX 8nzM6CkK6Fkq9f7MquhcVN2M8Cjd+t/HWlWyShEs/sH2CZXm2MM+c1PlUxwB3mfJ GAiIGvLm5TcPe63PmjmuQXqvgc0nTfDCj9bSIQbRigr0f7VwDEbGpOtrIpkyMxNG 9h433SKZaRfMx282IPc1vIiXY6sxezG+CIwTq+0IwhZgqPMWz3uVzgJniFmu5rMa nfu6q7Pqen/w660EbRrVPjeJr46fT7gIslawauWD/X/99SAbZrQs0w5SQBcpE4RN ILsOLgU95cHcrBkPQg9R =6Lf/ -----END PGP SIGNATURE----- --LQQvF5v7Jh3duU4E--