[ovirt-users] Why RAW images when using GlusterFS?

Hello, Amongst others, I have one 3.6 DC working very well since years and all based on GlusterFS. When having a close look (qemu-img info) on the images, I see their format is all RAW and not QCOW2. I never noticed or bothered before, but I'm wondering : - is it by design? - it is something we can change (I'd prefer qcow2) - it there some limitations? And finally, I have the same questions about NFS storage domains. Thank you. -- Nicolas ECARNOT