KVM: 0.905
network: 0.865
other: 0.831
device: 0.795
performance: 0.692
semantic: 0.489
files: 0.453
graphic: 0.383
permissions: 0.344
boot: 0.341
debug: 0.327
vnc: 0.323
socket: 0.286
PID: 0.182

kvm rbd driver (and maybe others, i.e. qcow2, qed and so on)  does not report DISCARD-ZERO flag