Re: [libvirt-users] Create qcow2 v3 volumes via libvirt
On Tue, May 01, 2018 at 12:35:05PM +0200, Gianluca Cecchi wrote:
On Tue, May 1, 2018 at 10:45 AM, Daniel P. Berrangé
<berrange(a)redhat.com>
wrote:
> On Tue, Jan 30, 2018 at 01:17:21PM +0100, Gionatan Danti wrote:
> > Hi all,
> > on a fully patched CentOS 7.4 x86-64, I see the following behavior:
> >
> > - when creating a new volumes using vol-create-as, the resulting file is
> a
> > qcow2 version 2 (compat=0.10) file. Example:
> >
> > [root@gdanti-lenovo vmimages]# virsh vol-create-as default zzz.qcow2
> > 8589934592 --format=qcow2 --backing-vol /mnt/vmimages/centos6.img
> > Vol zzz.qcow2 created
>
> Yes, for sake of backcompat we default to v2 unless something
> requires v3. You can't use vol-create-as to create a v3 image,
> you need to use the XML input.
>
BTW: in virt-manager of CentOS 7.4 by default qcow2 disks (see below for
zzz3.qcow2) are created with compatibility 1.1 (probably indirectly because
of its lazy refcounts feature enabled, as Daniel wrote):
Yes, virt-manager explicitly turns on lazy refcounts if it sees a new
enough QEMU, so will get v3
Regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|