From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: Re: Avoiding I/O bottlenecks between VM's Date: Fri, 19 Sep 2008 15:41:46 -0300 Message-ID: <20080919184146.GA12928@dmt.cnet> References: <200809191126.09889.alberto@byu.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: "kvm@vger.kernel.org" To: Alberto =?iso-8859-1?Q?Trevi=F1o?= Return-path: Received: from mx1.redhat.com ([66.187.233.31]:42915 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752724AbYISSmq (ORCPT ); Fri, 19 Sep 2008 14:42:46 -0400 Content-Disposition: inline In-Reply-To: <200809191126.09889.alberto@byu.edu> Sender: kvm-owner@vger.kernel.org List-ID: Hi Alberto, On Fri, Sep 19, 2008 at 11:26:09AM -0600, Alberto Trevi=F1o wrote: > I am using KVM 69 and kernel 2.6.25.17 to host several VM's in a larg= e=20 > server. So far, everything has been great. Except I'm adding a Wind= ows=20 > Server VM that will run a SQL Server database. A few times I've noti= ced=20 > that I/O becomes a bottleneck for the VM and Windows VM freezes for a= few=20 > seconds. Oh well, no biggie. Except, every so often, these I/O bott= lenecks=20 > start to affect other VM's and they freeze as well for a few seconds.= I=20 > don't really care of one VM does so much I/O that it freezes itself=20 > temporarily. I just don't want I/O bottlenecks on one VM to affect o= ther=20 > VM's. >=20 > My questions are: >=20 > 1. Is this a problem anyone else has experienced and has it been fixe= d in a=20 > later KVM release? >=20 > 2. I'm using the CFQ scheduler. Would the deadline scheduler do a be= tter=20 > job? >=20 > 3. Any other suggestions to improve this problem? Are you using filesystem backed storage for the guest images or direct block device storage? I assume there's heavy write activity on the guests when these hangs happen? ext3 with ordered data mode has latency issues on fsync.