Mailing the story:
Installing A Bind9 Master/Slave DNS System
In this tutorial two Bind DNS servers will be installed, one as the master and the other as a slave server. For security reasons Bind9 will be chrooted in its own jail. Using two servers for a domain is a commonly used setup and in order to host your own domain you are required to have at least two domain servers. If one breaks, the other can continue to serve your domain.