libvirt users - May 2015 - snapshots and vmdk

Does libvirt support snapshotting when the virtual disk comes from a vmdk file?

http://wiki.libvirt.org/page/Snapshots#Desired_functionality seems to say no,
since it says "'virsh snapshot', which requires all disk images to
be qcow2".

OTOH, man virsh, http://libvirt.org/formatsnapshot.html, and
http://libvirt.org/formatdomain.html#elementsDisks seem to indicate more
flexibility, though I see nothing about vmdk.

If there is support for vmdk, is it just for external snapshots, or do internal
snapshots work?

Currently running libvirt 0.9.12, qemu-kvm 1.1.2 (though I could use vmware
workstation), linux kernel 3.2.0.

Thanks.
Ross Boylan

On Sat, May 30, 2015 at 02:35:51AM +0000, Boylan, Ross
wrote:
> Does libvirt support snapshotting when the virtual disk comes from a
> vmdk file?
>From my quick test (refer below), seems like you can at-least use VMDK
as a backing file.
> http://wiki.libvirt.org/page/Snapshots#Desired_functionality seems to
> say no, since it says "'virsh snapshot', which requires all
disk
> images to be qcow2".
>
> OTOH, man virsh, http://libvirt.org/formatsnapshot.html, and
> http://libvirt.org/formatdomain.html#elementsDisks seem to indicate
> more flexibility, though I see nothing about vmdk.
> 
> If there is support for vmdk, is it just for external snapshots, or do
> internal snapshots work?
>From my quick test (for offline disks with `qemu-img`), it does seem to
work:

    $ qemu-img create -f vmdk base.vmdk 1G

    $ qemu-img create -f qcow2 -o \
        'backing_file=./base.vmdk,backing_fmt=vmdk' ./overlay1.qcow2

    $ qemu-img info overlay1.qcow2 
    image: overlay1.qcow2
    file format: qcow2
    virtual size: 1.0G (1073741824 bytes)
    disk size: 196K
    cluster_size: 65536
    backing file: ./base.vmdk
    backing file format: vmdk
    Format specific information:
        compat: 1.1
        lazy refcounts: false


And, as near as I know, internal snapshots are a feature of qcow2 format.
> Currently running libvirt 0.9.12, qemu-kvm 1.1.2 (though I could use
> vmware workstation), linux kernel 3.2.0.
-- 
/kashyap

On Mon, Jun 01, 2015 at 11:24:49AM +0200, Kashyap Chamarthy
wrote:
> On Sat, May 30, 2015 at 02:35:51AM +0000, Boylan, Ross wrote:
> > Does libvirt support snapshotting when the virtual disk comes from a
> > vmdk file?
Also, Stefan Hajnoczi from the QEMU project, points out:

    QEMU's implementations of all formats besides raw, qcow2, and qed
    are designed for import/export.  They are not designed for
    high-performance parallel I/O which you want for running guests. So
    it works but it can be much slower than using raw/qcow2 only.

    So it works but it can be much slower than using raw/qcow2 only.


-- 
/kashyap