From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: Better to use iSCSI on host or guest? Date: Mon, 13 Jun 2011 19:33:48 +0300 Message-ID: <4DF63BEC.2020809@redhat.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm To: Emmanuel Noobadmin Return-path: Received: from mx1.redhat.com ([209.132.183.28]:53268 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753850Ab1FMQdx (ORCPT ); Mon, 13 Jun 2011 12:33:53 -0400 In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On 06/13/2011 07:05 PM, Emmanuel Noobadmin wrote: > I'm planning to use iSCSI targets (over gigabit VLANs) for KVM guest > disks. The question I'm wondering about is whether it's better to md > (multi-path + mirror) the iSCSI targets on the host, then create LVM > partitions for the guests. Or to directly md the iSCSI targets within > the guest. > > On one hand I think it would be slower to process the additional > layers in the guest, but on the other hand, readings seems to indicate > that the kernel is able to perform better disk i/o if it's aware of > multiple disks rather than just seeing a single disk. > > I've not been able to find any definitive article/data on how these > might balance out. Would anybody in the list have a good idea which > way is better in terms of i/o performance? My gut feeling is to do iscsi in the host. I guess it's best to measure though. Please post your findings if you do that. -- error compiling committee.c: too many arguments to function