I just realized that when I change compatibility level to 4.3 under edit cluster settings it is automatically switching CPU type from "Intel SandyBridge IBRS Family" to "Intel Nahalem Family". I believe the CPU type change is what is requiring all hosts to be in maintenance mode. My question is, is the change of the family type correct or is it a different family type being selected due to a bug or some other issue?
I'm also a bit unclear about updating to 4.3 cluster level. I have a 3 host HCI setup which I just updated to 4.3 manually. I upgraded engine to 4.3 then upgraded each of the three hosts to ovirt node 4.3. I still need to change cluster/data centre compatibility level to 4.3. If I try to change cluster compatibility level to 4.3 it tells me that all hosts need to be in maintenance to do so (does this mean I need to shut down all VMs and put each host in maintenance?)