Fuel should restrict to deploy any other services and roles(like Zabbix, LMA, Mongo and etc)

[Andrey Epifanov]

Controllers should be standalone hosts and other third-party services should not impact the Core OpenStack services (CPU, RAM, Disk, Network, etc)

The Other option to show a big red warning with a description of the consequences and confirmation about awareness of these risks.

[Dmitry Pyzhov (dpyzhov)]

The issue cannot have critical priority according our criteria: https://wiki.openstack.org/wiki/Fuel/How_to_contribute#Triaging_the_bugs_in_the_Fuel_deployment_process
Moreover, it is intended behaviour, we allow user to combine roles according his/her needs.

[Roman Rufanov (rrufanov)]

Marking this as High priority since it brought down multiple Production clouds. We are fine that you allow to combine this - but at least give a user clear warning that strongly not advised since it will lead to performance issuess