From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dor Laor Subject: Re: virtio disk slower than IDE? Date: Mon, 16 Nov 2009 23:09:06 +0200 Message-ID: <4B01BF72.9020008@redhat.com> References: <4AFEBD59.2090002@bobich.net> <4AFFCF18.1080509@redhat.com> <4AFFED49.9010305@bobich.net> <4AFFFF0D.3090608@redhat.com> <4B00851F.5060206@bobich.net> <4B0195E5.2090206@messageone.com> Reply-To: dlaor@redhat.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Gordan Bobic , kvm@vger.kernel.org To: Charles Duffy Return-path: Received: from mx1.redhat.com ([209.132.183.28]:41647 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754042AbZKPVJM (ORCPT ); Mon, 16 Nov 2009 16:09:12 -0500 In-Reply-To: <4B0195E5.2090206@messageone.com> Sender: kvm-owner@vger.kernel.org List-ID: On 11/16/2009 08:11 PM, Charles Duffy wrote: > Gordan Bobic wrote: >>> Lastly, do you use cache=wb on qemu? it's just a fun mode, we use >>> cache=off only. >> >> I don't see the option being set in the logs, so I'd guess it's >> whatever qemu-kvm defaults to. > > You can set this through libvirt by putting an element such as the > following within your element: > > It's not needed on rhel5.4 qemu - we have cache=none as a default > > (Setting the type is preferred to avoid security issues wherein a guest > writes an arbitrary qcow2 header to the beginning of a raw disk, reboots > and allows qemu's autodetection to decide that this formerly-raw disk > should now be treated as a delta against a file they otherwise might not > have access to read; as such, it's particularly important if you intend > that the type be raw). > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html