From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dieter Kasper Subject: Re: RBD performance - tuning hints / major slowdown effect(s) Date: Fri, 31 Aug 2012 11:49:26 +0200 Message-ID: <20120831094926.GA30653@oder.kd-bie.de> References: <503F91EF.7020807@inktank.com> <1ab6cbb8-de0c-4d24-953b-98eced2f4ae2@mailpro> <24E144B8C0207547AD09C467A8259F755760304F@lisa.maurer-it.com> <50407A62.1020208@catalyst.net.nz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8BIT Return-path: Received: from smtpa1.mediabeam.com ([194.25.41.13]:53329 "EHLO smtpa1.mediabeam.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751820Ab2HaJtw convert rfc822-to-8bit (ORCPT ); Fri, 31 Aug 2012 05:49:52 -0400 Content-Disposition: inline In-Reply-To: <50407A62.1020208@catalyst.net.nz> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Mark Kirkwood Cc: Dietmar Maurer , Alexandre DERUMIER , Josh Durgin , "ceph-devel@vger.kernel.org" , Andreas Bluemle Mark, Inktank, OK, it is very likely that 'sync_file_range' is not the major slowdown 'culprit'. But, which areas (design, current implementation, protocol, interconnect, tuning parameter, ...) would you rate as 'major slowdown effect(s)' ? Best Regards, -Dieter On Fri, Aug 31, 2012 at 08:48:34PM +1200, Mark Kirkwood wrote: > On 31/08/12 20:11, Dietmar Maurer wrote: > >>>RBD waits for the data to be on disk on all replicas. It's pretty easy > >>>to relax this to in memory on all replicas, but there's no option for > >>>that right now. > >I thought that is dangerous, because you can loose data? > >N???????????????r??????y?????????b???X????????v???^???)??{.n???+?????????z???]z???{ay??????????,j??????f?????????h?????????z??????w????????? ?????????j:+v?????????w???j???m????????????????????????zZ+????????j"??????!tml= > > And it is not immediately obvious that this is the bottleneck - from > what I can see the 'sync' call being used (sync_file_range) is > extremely fast and is *not* the major slowdown effect... > > Regards > > Mark >