Support qcow datastore for Ceph storage

[draggeta]

The required feature described as a wish

As a User/Admin/Operator I would like to have support for the data-file functionality of libvirt 10.10 supported on newer hosts. This way one would be able to use a lot of different backup solutions such as virtnbdbackup to back up VMs running on a Ceph primary storage.

https://www.mail-archive.com/devel@lists.libvirt.org/msg07367.html

• qemu: Support for the 'data-file' QCOW2 image feature

The QEMU hypervisor driver now supports QCOW2 images with 'data-file'
feature present (both when probing form the image itself and when specified
explicitly via <dataStore> element). This can be useful when it's
required to keep data "raw" on disk, but the use case requires features
of the QCOW2 format such as incremental backups.

There are probably a lot of things to take into account, but it would still be a great improvement.

[boring-cyborg]

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[DaanHoogland]

@draggeta , will you do any further analysis on the feature/possibility?

[draggeta]

I wouldn't mind, but I'm not sure if this is something the project wants. I can imagine that CS maybe wants to keep things as uniform as possible and not introduce things that can cause breakages in mixed OS cluster or how to do this on existing VMs.