Have you ever wondered how people plan for the capacity of a system? This presentation tries to explain how to do it. It is definitely an art, but the tools used here will help you learn how to do it with logic and reason rather than hopeful optimism. That should help you keep from under or over sizing the systems you build in the future.
Systemd is the new system that Ubuntu is using to control the boot process. It's what makes the systems boot faster and cleaner. It does things dramatically differently than the older init.d system did.