

I edited, since it was ambiguous. I think you only need zfs if you want replication, cold migrations should be fine without it.
Removing nodes from clusters is fine. It’s not really encouraged, but if a node fails you have to be able to remove it, so it’s possible.
If your request is showing up in nginx’s log, it means you can reach nginx. The upstream is where nginx is going to get the content you want. In your case, that should be the other containers.