[ovirt-users] How to upgrade my cluster to 4.4 without pain (it will be useful not only to me)

We have four hosts with self-hosted engines. Installed version of the engine 4.3.9. I have the power reserve to migrate all virtual machines to three hosts and spend on construction on the remaining host. I really want someone to help me make a plan to upgrade and upgrade to version 4.4 without pain. I will describe the configuration in more detail: 4 hosts where ovirt node 4.3.9 was deployed, and then one of them has an ovirt engine with a control panel deployed. In the process the storage was added and everything works fine. In the ovirt settings, when adding a host, I deployed a backup engine (gray crown icon). Backup engine is available on each host and was specially tested when one of the hosts was turned off. "Now as I think it will update and there will be questions immediately." 1. My first step is to remove a free host from the control panel and deploy ovirt node (4.4) on it 2. Next, the question arises: since I have to restore the new engine from backup 4.3.9, will it not show a version incompatibility? 3. If I need to restore the backup, then logically I have to disable all my engines and then restore? 4. When I restore the engine, will my hosts and virtual machines go nowhere? Will hosts with old version 4.3.9 be available? Please do not criticize me and understand correctly - there are over 100 virtual machines with important data. A rough plan could help me minimize serious errors. In addition, I could share my upgrade experience with the real configuration, which could help both developers and administrators. Regards!