11:21 a.m.
I have an oVirt engine node that currently runs the system on a qcow2
based virtual disk, and an NFS export volume on RAW. I'd like to take
a snapshot before a somewhat risky upgrade of oVirt and can't with the
raw image attached.
Looking at the documentation for the snapshot XML, I created this XML
file for the snapshot
<domainsnapshot>
<name>20120802</name>
<description>oVirt 3.1 upgrade</description>
<disks>
<disk name='vda' snapshot='yes' />
<disk name='vdb' snapshot='no' />
</disks>
</domainsnapshot>
When I try the snapshot I get this error...
# virsh snapshot-create dc-vmarchitect dc-vmarchitect_ss.xml
error: argument unsupported: unable to handle disk requests in snapshot
This occurred on both libvirt-0.9.4 and after an upgrade to libvirt-0.9.10
Current system is CentOS 6.2 with 6.3 versions of qemu/libvirt
qemu-kvm-0.12.1.2-2.295.el6_3.1.x86_64
qemu-img-0.12.1.2-2.295.el6_3.1.x86_64
libvirt-client-0.9.10-21.el6_3.3.x86_64
libvirt-python-0.9.10-21.el6_3.3.x86_64
libvirt-0.9.10-21.el6_3.3.x86_64
According to the documentation,
http://libvirt.org/formatsnapshot.html, the disk features should be
available since 0.9.5. Is this still missing or have I created an
invalid XML?
Thanks
- Trey
11:36 a.m.
On 08/02/2012 10:21 AM, Trey Dockendorf wrote:
I have an oVirt engine node that currently runs the system on a
qcow2
based virtual disk, and an NFS export volume on RAW. I'd like to take
a snapshot before a somewhat risky upgrade of oVirt and can't with the
raw image attached.
Looking at the documentation for the snapshot XML, I created this XML
file for the snapshot
<domainsnapshot>
<name>20120802</name>
<description>oVirt 3.1 upgrade</description>
<disks>
<disk name='vda' snapshot='yes' />
<disk name='vdb' snapshot='no' />
</disks>
</domainsnapshot>
When I try the snapshot I get this error...
# virsh snapshot-create dc-vmarchitect dc-vmarchitect_ss.xml
error: argument unsupported: unable to handle disk requests in snapshot
Try again with:
virsh snapshot-create --disk-only dc-vmarchitect dc-vmarchitect_ss.xml
The --disk-only parameter is essential, as the current code base can
only choose between a system checkpoint (disk state and ram state,
stored internally into required qcow2; takes several seconds and the
guest is paused during the action) or disk-only external (disk state
only, external files, does not require qcow2 at the starting point;
completes very quickly).
I have tested that qemu will support the notion of an external system
checkpoint (disk state and ram state, stored into external files, does
not require qcow2 at the starting point), but have to still write the
patches to actually expose that mode; I still have time to get something
proposed before the 0.10.0 feature freeze, so I'll see what I can do.
This third mode of snapshots would not use the --disk-only flag, and
would take several seconds like the existing system checkpoint but has
the advantage that the guest is running during the bulk of the operation.
According to the documentation,
http://libvirt.org/formatsnapshot.html, the disk features should be
available since 0.9.5. Is this still missing or have I created an
invalid XML?
Neither - you just missed the --disk-only flag.
--
Eric Blake eblake(a)redhat.com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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Trey Dockendorf