I use OpenmediaVault inside a Proxmox VM with 6 physical disks added as virtio drives. S.M.A.R.T does not work, using the -d option does not work either, gives me the same result as post #35.
When I first installed OMV, S.M.A.R.T worked as it should. It was not until I upgraded from Proxmox 3.4 to 4.2 that I noticed S.M.A.R.T no longer functioned.
Now I don't know if its because of the Proxmox upgrade, I only noticed it since I had to reattach the physical drives again since their IDs changed. The fault might have been there for awhile before the Proxmox upgrade.
If specify SCSI instead of virtio when adding the drives, S.M.A.R.T works but will sometime hang OMV on boot for some reason.