The Ponyland cluster is a powerful tool for getting your calculations done quickly, in particular if you use multiple cores or even multiple ponies simultaneously. This power, however, is not unlimited: if you use all cores on all ponies, you will slow down other jobs by other people that are running at that same time.
At some other clusters SGE is used to divide the resources. For Ponyland, however, we decided we do not want to force people into using SGE for a number of reasons, the most important ones being the desire to work from a local scratch disk for faster I/O, or in a more interactive session using screen or tmux.
To make sure this freedom to avoid SGE does not mean everybody tries to use all of the ponies all the time, a number of guidelines have been composed:
htop(a little more visual) to see if a server has sufficient resources, and they monitor their processes as they run.