snapshot=on fails with non file-based storage
The snapshot=on option doesn't work with an nbd block device:
-device scsi-hd,drive=hd0 \
gives the error:
qemu-system-x86_64: -drive file=nbd:
If you remove the snapshot=on flag, it works (although that of course means that the block device is writable which we don't want).
Previously reported here:
and I can confirm this still happens in qemu 1.4.0.