Usage guidelines

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 Slurm is used to divide the resources. For Ponyland, however, we decided we do not want to force people into using Slurm 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 Slurm does not mean everybody tries to use all of the ponies all the time, a number of guidelines have been composed:

1. Non-Slurm users always check top or htop (a little more visual) to see if a server has sufficient resources, and they monitor their processes as they run.
2. No single user takes all the resources of a single node (or all nodes). System load shouldn't exceed the number of cores (32 with hyperthreading).
3. Slurm users keep within the Slurm-constraints.
4. Communicate and coordinate with others running things (our IRC chat is a good medium for that ;) ).. even Slurm can't replace communication.
5. Never use Applejack or Lightning for experiments. These ponies are reserved for websites and webdemos.