On Mon, Mar 04, 2013 at 03:04:53PM +0100, Kevin Wolf wrote: > Am 04.03.2013 um 14:09 hat Daniel P. Berrange geschrieben: > > On Mon, Mar 04, 2013 at 01:58:12PM +0100, Ján Tomko wrote: > > > Before posting another version of my patches [1], attempting to add > > > support for the new qcow format to libvirt, I would like to know if this > > > sounds reasonable: > > > > > > A new format named 'qcow3' would be added, along with a <features> > > > sub-element for target. > > > > > > <volume> > > > <name>qcow3test</name> > > > <source> > > > </source> > > > <capacity unit='GiB'>8</capacity> > > > <target> > > > <path>/var/lib/libvirt/images/qcow3test</path> > > > <format type='qcow3'/> > > > <features> > > > <lazy_refcounts/> > > > </features> > > > </target> > > > </volume> > > > > > > I think that libvirt shouldn't care if the features are compatible or > > > incompatible, as we don't know what features are supported by the > > > hypervisor. Would the features be any good as tri-state (on, off, default?). > > > > > > While the qcow3 format is handled by the qcow2 driver in QEMU, > > > <driver name='qemu' type='qcow2'/> should be enough for domains, > > > > We should use qcow3 everywhere IMHO, regardless of whether qcow2 > > technically works in this context. > > I think it makes much more sense to deal with it the way qemu does > instead of inventing new names. This has much more of an (incompatible) > feature flag than of a different image format. So to fit it in your > proposed syntax: The issue is that QEMU is not the only thing that implements the qcow format. There are a number of other impls out there, and we can't just assume that they will all be providing a qcow2 driver that automagically opens a qcow3 image format. Just in the same way we didn't assume that a 'qcow' (version 1) driver would open a version 2 image. It so happens that with QEMU if you specify format=qcow2 and give it a qcow3 image, QEMU will open it, but libvirt can't assume that, since this is a mere implementation detail. Hence libvirt must explicitly refer to 'qcow3' in the XML and map it to qcow2 if applicable when talking to QEMU. > But I guess you call all VMDKs just "vmdk", despite the fact that they > are really just a collection of different subformats. Right? Yes, but that is really a bug in our representation of vmdk. 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 :| -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list