are btrfs snapshot helpful for backing up kvm qcow2 vm?

[Francesco Morosinotto <jlord87@gmail.com>]

Hi guys,

I need to improve the backup strategy of my vms; At the moment I backup the machines once a week by stopping them, making a snapshot, exporting the xml descriptor file and backing up these files.

I would prefer a daily online backup solution that allows me to take a snapshot with a minimum downtime.

That's why I was planning to switch from etx4 to btrfs;
my project will be to  pause the vm, dump the memory and the xml descriptor file, make a snapshot of the subvolume storing the qcow2 file and after that resuming the machine.

does this project makes any sense? What about performance? Am I going to experience bad performance having qcow2 over btrfs?
I read on some old (two years) posts that btrfs was having bad fragmentation when dealing with qcow2 files, is this still happening?

Thank you

Francesco