We have MAAS 3.4/stable (3.4.0-14321-g.1027c7664) deployed to a lab environment as well as starting to roll it out worldwide in production. In the lab we were able to successfully test a full HA setup with 2 region controllers and 2 rack controllers providing load balancing, but most of our environments are small colo datacenter racks where we cannot fit multiple MAAS rack controllers in each physical rack (due to power budget and/or space concerns). Our standard architecture (prior to MAAS) uses IP helpers (to relay DHCP from one colo to another within the same geographic area), and to load balance between 2 in order to provide resilience in case one goes down.
We have MAAS relaying DHCP services from a rack controller in each geographic area and it works well to serve multiple subnets, but unlike in the lab where we were presented with the two drop-down menus to configure primary and secondary, we can’t find a away to add a second rack controller when using relayed DHCP in order to provide high availability.
Is there a way to enable HA DHCP for relayed subnets, or is this restricted to a single rack server in MAAS? If it isn’t restricted, how do we go about enabling it, and if it is, how to we achieve proper HA resiliency?