I did this previously with a server on ubuntu 16.04 and targetcli. It worked and is still online today. I'm in need of more storage so I decided to make another machine with ubuntu 18.04 and targetcli-fb. The problem I have is that I cannot add the server to the failover cluster.
When I add the disk to the cluster it says the disk is not ready. On the event log of the cluster it gives IDs : 1793, 1069, 1205 and 1254 When I use the validation assistant it fails the "Validate SCSI-3 Persistent Reservation", something about "REGISTER AND IGNORE EXISTING" failing.
I do not remember what was done with the previous storage server and cannot remember if there was a configuration to make the disk able to go offline on one node if another brought it online as it asks to be done.
Disk is currently offline on all nodes, partition style is GPT and really should be able to connect, but it just does not.