From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Daniel P. Berrange" Subject: Re: The two image formats called qcow Date: Wed, 26 Mar 2008 13:23:16 +0000 Message-ID: <20080326132316.GB27082@redhat.com> References: <47EA0E3E.4030200@suse.de> Reply-To: "Daniel P. Berrange" Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <47EA0E3E.4030200@suse.de> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Kevin Wolf Cc: xen-devel@lists.xensource.com, Keir Fraser , Otavio Salvador List-Id: xen-devel@lists.xenproject.org On Wed, Mar 26, 2008 at 09:50:06AM +0100, Kevin Wolf wrote: > Keir Fraser schrieb: > > It's tricky where users' non-volatile storage is concerned though. Other > > than that I would say the bug should be fixed immediately. Is there an easy > > way to detect with reasonable reliability whether we have an old or new > > image? Failing that we may have to provide a tool to convert old images to > > new format. > > Something like "that number looks too big, it be must little endian" > could easily turn into "that harddisk looks big, let's break the image", > I suspect. > > However, I just noticed that the tapdisk qcow driver writes an extended > Xen-specific header to the image file. This should be reliable enough to > detect tapdisk images. > > Is it an option to convert broken images to big endian when it is opened > for the first time in ioemu? In this case, the fix for older versions > could be in one place at least instead of being scattered over the whole > file. Then you wouldn't be able to open such a file with tapdisk again, > though. I don't like the idea of secretly migrating them to the fixed disk format without admin interaction / confirmation. If we can detect the old style disk format, then perhaps we could put a check into the hotplug scripts. That way, when the user tries to start a guest with the old broken format, we could prevent the guest starting and show them a error message. Then can then run the conversion tool to fix the format & start the guest again. Dan -- |: Red Hat, Engineering, Boston -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://ovirt.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|