From mboxrd@z Thu Jan 1 00:00:00 1970 From: Charles Duffy Subject: Re: virtio disk slower than IDE? Date: Mon, 16 Nov 2009 12:11:49 -0600 Message-ID: <4B0195E5.2090206@messageone.com> References: <4AFEBD59.2090002@bobich.net> <4AFFCF18.1080509@redhat.com> <4AFFED49.9010305@bobich.net> <4AFFFF0D.3090608@redhat.com> <4B00851F.5060206@bobich.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Gordan Bobic Return-path: Received: from mail-gx0-f226.google.com ([209.85.217.226]:44236 "EHLO mail-gx0-f226.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751825AbZKPSNv (ORCPT ); Mon, 16 Nov 2009 13:13:51 -0500 Received: by gxk26 with SMTP id 26so1023032gxk.1 for ; Mon, 16 Nov 2009 10:13:56 -0800 (PST) In-Reply-To: <4B00851F.5060206@bobich.net> Sender: kvm-owner@vger.kernel.org List-ID: 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: (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).