[Qemu-devel] QCOW2 multiple disk (not VM) snapshots

[Mike Sun]

Hi,

For a research project, we've been doing a bit of hacking with Xen and
utilize QCOW disk images as our VBDs. One intriguing thing about the
QCOW2 format was support for multiple disk snapshots. Unfortunately,
it seems from what I've been able to glean that support for multiple
snapshots within a QCOW2 image is really only supported by QEMU's VM
snapshot feature. Since I'm using Xen and only use QCOW2 disk images,
I was wondering if there was any way from a tool such as 'qemu-img' to
take snapshots of the QCOW2 disk image only and not through the
general QEMU VM snapshot?

Originally, I had thought that the CoW functionality provided by QCOW
disks could be used to implement snapshots, but I learned that this
wasn't achievable since QCOW disks cannot recursively back themselves.

Thanks,
Mike