Hello,
currently running Puppet and Foreman on a single host as a development
environment.
We are aiming to manage about 3000 Nodes - 20 classes per node - 1-2 hours
intervall - in production.
Can this be aceived on a single host with multiple CPUs .or do we nee a
distributed environment.
thanks
There are so many variables involved in this sort of calculation, so
it's really difficult to say (check the puppet-users archive for many
such discussions).
As a rule of thumb, I tend to expect a well-specced puppetmaster to
handle ~1000 hosts comfortably, using the default run interval of
30mins. If your extrapolate that to a well distribted 2 hour window,
you get ~4k hosts, so you should be ok.
This is all using numbers pulled out of thin air, of course 
If you
hit issues, you can always drop the run interval until you can get
more hardware in.
HTH,
Greg