In the WebUI, I see all 3 hosts marked as "up". But when I run hosted-engine --vm-status (or migrate the hosted engine), only the first (original deployed) host is available. I tried "reinstalling" (from the WebUI) the two hosts, no errors, no change. I tried upgrading the cluster again, host 2 / 3 (the "missing" hosts) upgrade is successful; hosts1 fails (cannot migrate the hosted engine).
Start debugging from the hosts that are not seen via "hosted-engine -- vm-status". There are 2 log files to check: /var/log/ovirt-hosted-engine-ha/{broker,agent}.log Just check what they are complaining about. Also , you need both ovirt-ha-broker.service and ovirt-ha-agent.service up and running. If there is an issue, the ovirt-ha-agent is being restarted (so it's expected behaviour). Usually the broker should stop complaining and then the agent will kick in. Best Regards, Strahil Nikolov