This will be a monster project if you have a large infrastructure. Check this first to get an idea of the files you’ll need to migrate:
So a few things to know, Icinga installs on Debian under the user nagios and on centos as the user icinga, keep that in mind when fixing permissions. If you change the master’s hostname, you’re probably going to be in certificate hell, but someone else could correct me if I’m wrong. I suppose it might be possible to generate a new cert from the same ca before updating zones.conf on every node in the master zone. Definitely build a small distributed setup in a qa environment and run through all of this there first.
I run postgresql and influxdb on a pair dedicated servers with fast ssds, soft raid and replication. I’m not having performance problems personally. As long as they’re close together all should be fine.
This whole thing will possibly cause you over an hour of downtime on your monitoring depending on how fast your automation approach is. Make sure you have some help watching out for issues in your environment during it.