From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Priebe Subject: Re: default filestore max sync interval Date: Tue, 29 Apr 2014 22:36:55 +0200 Message-ID: <53600D67.1000501@profihost.ag> References: <3B502314D0477C4F9478870C279E14E60118278B1F@CERNXCHG51.cern.ch> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ph.de-nserver.de ([85.158.179.214]:55688 "EHLO mail-ph.de-nserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752836AbaD2Unb (ORCPT ); Tue, 29 Apr 2014 16:43:31 -0400 In-Reply-To: <3B502314D0477C4F9478870C279E14E60118278B1F@CERNXCHG51.cern.ch> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Dan Van Der Ster , "ceph-devel@vger.kernel.org" Hi Dan, Am 29.04.2014 22:10, schrieb Dan Van Der Ster: > Hi all, > Why is the default max sync interval only 5 seconds? > > Today we realized what a huge difference that increasing this to 30 or 60s can do for the small write latency. Basically, with a 5s interval our 4k write latency is above 30-35ms and once we increase it to 30s we can get under 10ms (using spinning disks for journal and data.) > > See the attached plot for the affect of this on a running cluster (the plot shows the max, avg, min write latency from a short rados bench every 10 mins). The change from 5s to 60s was applied at noon today. (And our journals are large enough, don't worry). > > In the interest of having sensible defaults, is there any reason not to increase this to 30s? I was playing with them too but didn't get any viewable results. How do you get / graph the ceph latency? Greets, Stefan