Hi Tim,
HA, HCI and failover either require or at least benefit from consistent storage.
The original NFS reduce the risk of inconsistency to single files, Gluster puts the onus
of consistency mostly the clients and I guess Ceph is similar.
iSCSI has been described as a bit the worst of everything in storage and I can appreciate
that view in a HA scenario because it doesn't help with consistency.
Of course, its block layer abstraction isn't really that different from SAN or NFS 4.x
object storage.
I last experimented with iSCSI 20 years ago, mostly because it seemed so great for booting
even less cooperative diskless hosts than Sun workstations over the network.
But if I had a reliable TrueNAS and wanted to run oVirt, I'd just go with NFS.
AFAIK oVirt was born on SAN but with SAN outside of oVirt's purvue. So if your iSCSI
setup behaves like a SAN, oVirt should be easy to get going, but I've never tried
myself.
And the lack of tried and tested tutorials or videos from 20 different sources might be
the reason oVirt didn't quite push out everybody else.