What is the risk of running 2 Postgresql instances of the same version on the same server?

Question

PostgreSQL

What problems can arise in operation?
What problems can arise during replication?
Is it enough to set up different ports and folders for the database to make 2 services work with postgresql?

Answer 1

None. None at all. This is a regular option, there is even a regular setting cluster_name, which will be displayed in the list of processes for easy identification of which particular cluster you are looking at. For debian/ubuntu, it is controlled by standard pg_ctlcluster utilities.
Need different datadir and non-overlapping network settings