Over 10 yrs ago, I tried an experiment to see if a raspberry pi model B could cope as primary nameserver for our small school. It ran debian with bind in a chroot jail, that I learned from a howto on tldp. Yesterday was it's last day of service. Of course I upgraded it along the way, and every 3 yrs or so did a complete reinstall on a new sd card (and with a new tutorial). The secondary ns at OCN obviously helped a lot, but I was very pleased with what could be achieved with such a lowly machine. Here you can see it in action, ziptied to a hub and running debian 11.