From mboxrd@z Thu Jan 1 00:00:00 1970 From: Martin Troester Subject: Xen 3.4.1 and QCOW - sparse backing file support gone forever? Date: Thu, 24 Sep 2009 22:43:10 +0200 Message-ID: <4ABBD9DE.5090103@web.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org Hi, I'd like to get some hints on using or migrating QCOW images with sparse backing files. In February, I posted a question about this and got some hints by Ian which generally state this support was removed/disabled due to a possible security issue. For the full thread, please see the post at http://lists.xensource.com/archives/html/xen-devel/2009-02/msg00150.html So with Xen 3.4.1 being released already, it seems like I am stuck now with my chosen approach of having a qcow file which points to another (non-raw) qcow backing file. This does not boot, everything looks as in the February Xen 3.3 posting. Ian, these comments from your last response particularly are of interest to me: > So I `fixed' this by making all backing files of cow images always be > treated as raw images. (In upstream this is being fixed by adding > more metadata to the data format but the exact syntax is still > settling down and this change comes too late for Xen 3.3.) Can you or some qemu developer reading this please explain if this code actually made it into 3.4.1, and if yes, how I would migrate my existing files to contain this "more metadata" to be working again? If that's not in, is there any plan how to deal with scenarios like mine? Especially, is there way to convert my images to some usable format for not having to stick to Xen 3.2.1? Or is it just too exotic so that I throw everything away and think of something else? (I am still thinking that stacking qcow images is not the most stupid thing to do...) Thanks for any support and hints on this topic! Regards, Martin