From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:54354) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QjTEj-0005iy-QM for qemu-devel@nongnu.org; Wed, 20 Jul 2011 05:38:43 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QjTEb-0005yO-N3 for qemu-devel@nongnu.org; Wed, 20 Jul 2011 05:38:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33381) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QjTEa-0005y2-SE for qemu-devel@nongnu.org; Wed, 20 Jul 2011 05:38:29 -0400 Date: Wed, 20 Jul 2011 10:38:06 +0100 From: "Daniel P. Berrange" Message-ID: <20110720093806.GB5015@redhat.com> References: <4E253136.4080509@redhat.com> <4E258635.2040108@redhat.com> <4E258D70.6000205@redhat.com> <4E25902D.2000403@redhat.com> <4E2593B0.1030508@redhat.com> <4E2594FB.4050203@redhat.com> <20110719164755.GF12026@redhat.com> <4E269149.4090904@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <4E269149.4090904@redhat.com> Subject: Re: [Qemu-devel] live snapshot wiki updated Reply-To: "Daniel P. Berrange" List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jes Sorensen Cc: "libvir-list@redhat.com" , Stefan Hajnoczi , Eric Blake , QEMU Developers , Stefan Hajnoczi On Wed, Jul 20, 2011 at 10:26:49AM +0200, Jes Sorensen wrote: > On 07/19/11 18:47, Daniel P. Berrange wrote: > > On Tue, Jul 19, 2011 at 04:30:19PM +0200, Jes Sorensen wrote: > >> On 07/19/11 16:24, Eric Blake wrote: > >>> Besides, I feel that having a well-documented file format, so that > >>> independent applications can both parse the same file with the same > >>> semantics by obeying the file format specification, is a good design goal. > >> > >> We all know that documentation is rarely uptodate, new features may not > >> get added and libvirt will never be able to keep up. The driver for a > >> file format belongs in QEMU and nowhere else. > > > > This would be possible if QEMU to provide a libblockformat.so library > > which allowed apps to extract metadata from file formats using a stable > > API. > > There is no reason for libvirt or any external process to mess about > with the internals of image files. You have the same problem if the > image file is encrypted. Just repeating "libvirt doesn't need todo this" many times doesn't make it true. I have described why we need to read the disk image to determine its backing files ahead of QEMU being launched quite clearly. Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|