[libvirt-users] snapshots and vmdk

[Kashyap Chamarthy]

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