Rolling Out Unattended Debian Installations (Part 1) - page 4
Requirements and Overview
FAI comes with an excellent manual, which is also installed to /usr/share/doc/fai/fai-guide.html. The /usr/share/doc/fai/ directory is full of scripts and configuration examples.
Troubleshooting help is here.
FAI uses standard Linux utilities glued together with Perl and Bash scripts, so you can refer to their individual man pages, such as rsync, debmirror, NFS, and so forth.
See Information for mirror owners for more information on mirror sizes, and useful resources on mirroring.