If the problem is anything like this: https://www.reddit.com/r/btrfs/comments/fcntc6/qcow2_on_btrfs_performance/ https://www.reddit.com/r/btrfs/comments/fcntc6

If the problem is anything like this: https://www.reddit.com/r/btrfs/comments/fcntc6/qcow2_on_btrfs_performance/ https://www.reddit.com/r/btrfs/comments/fcntc6/qcow2_on_btrf... You can either make a sub volume and mount it with nocow or set the +C file attribute to disable CoW: http://blog.jim.nz/2015/12/04/btrfs-subvolume-with-nocow.html http://blog.jim.nz/2015/12/04/btrfs-subvolume-with-nocow.htm... Doesn’t really look like nilfs2 has this kind of flexibility, though