i implemented a EM Cluster with 4000+ agents and there are a few things so far to mention:
- the initial loading of all the agents in to the client can be a problem
- when the agents start loadbalancing it is as well a massive load and could lead to problems
- if you let the mom loadbalance freely you might end up with 10x the number you calculated from a historical count perspective per collector
- the agents really need to be controlled to not suddenly deliver massive amount of metrics
- the historical metric count has an impact as well depending on how long you store the metric data and over time the enviornment could get slower
- as with every sizing give enough power and headroom for the collectors and mom to work with
but in general it works well and depending on the issue you are face you might have to analyze, configure and test things no one else did before not even CA