Snapshots (with direct attached LUN's)

Snapshots seem to work OK for anything using the internal data domain as it's all controlled via LVM, however, not the case for direct attached LUN's.

I assume snapshot capability does not work for direct attached LUNs?

I've created a VM with a single direct attached LUN as the O/S disk. I then took a snapshot which shows as successful but what has it actually done as there is no snapshot of the LUN created (I don't see how there possibly could be??).

If it's only snapshotting the "Data Domain" images and there are none attached to a VM should it fail to create the snapshot and if there is a mix of "Data Domain" images and "direct attached LUN's" attached to a VM should there be a warning to say the snapshot will only include the "Data Domain" images?