Not specific to you IDO of choice (in this case IcingaDB), but your Redis and/or IcingaDB can live anywhere, as long as you can connect the correct Icinga related services to them.
For example, using the MySQL IDO, we connect Icinga2 to an
icinga2 database on
dbserver1.local and connect Icingaweb2 to an
icingaweb2 database that is also on
Similar as above – as long as your firewall rules across your network are correct, it doesn’t really matter where Redis lives (or any other IDO) as long all machines that you need to connect to it can reach it.
We use Centreon Plugins for a lot of things and have ~6 agents in two or three different US States connected all to the same Redis server.