Hello,
I noticed that the information on setting up Icinga HA clusters doesn’t mention what the practical (negative) consequences are of disabling enable_ha:
https://icinga.com/docs/icinga-2/latest/doc/14-features/#ido-database-db-ido
If one sets up two SQL servers without replication, how does Icinga deal with a situation where these are not in sync?
There you have the practical (negative) consequences, it does not. You simple will have two separate databases with redundant information relying on being the same, but if ever for some reason Icinga 2 did not sync this assumption will not be true. Most simple case I can think of are a connection loss exceeding the log_duration which is per default 1d.