OT - how to size/match multiple databases/apps for a single server

[Kevin Kempter <kevin(at)kevinkempterllc(dot)com>]

Hi List;

I have a client looking to host/co-locate multiple PostgreSQL clusters 
(inclusive of PL/pgSQL application code) per server. I did some co-location 
work several years back with one of the bigger telco's and remember there 
were dire consequences for not carefully evaluating the expected resource 
usage of each database/app and matching apps based on some common sense (i.e. 
match a memory intensive app with a CPU intensive app)

My question is:
Does anyone have any templates, guidelines, thoughts, etc with respect to how 
to eval and match multiple databases for a single server. Such as a checklist 
of resource items to look at and guidelines per how to line up db clusters 
that should play nicely together?

Thanks in advance...