$ sudo stat -f /var/lib/libvirt/images/green-nas_001.qed
  File: "/var/lib/libvirt/images/green-nas_001.qed"
    ID: 395065972ab3a079 Namelen: 255     Type: btrfs
Block size: 4096       Fundamental block size: 4096
Blocks: Total: 1951008512 Free: 1272515145 Available: 1271610545
Inodes: Total: 0          Free: 0