IRIDIA cluster installing an OS on the servers
You should install a Linux distribution on the servers. Debian has proved itself appropriate and the documentation here is based on Debian. So unless you are a very adventureous spirit with too much time on your hands, you should stick to Debian.
Install Debian in a minimal version
Notice that polyphemus has two NICs while majorana has three. The 100 Mbit NICs connects the servers to the world, so configure those if you do a network install.
Enable the Gigabit Ethernet NICs in:
After Debian has been installed move on to installing the cluster server daemons