Selection and Operation of Secondary DNS Servers
There are always lessons to learn from major incidents. For instance, outages like the one that the global hosting provider GoDaddy has suffered yesterday should remind us of how best online resources are deployed! A must-read RFC about the selection and operation of secondary DNS servers defines the best practices to set up a secondary DNS server for your domain. The Domain Name System requires that multiple servers exist for every delegated domain (zone). This RFC discusses both the physical and topological location of each server when selecting DNS secondary servers.
Read more here - http://blog.rootshell.be/2012/09/11/godaddy-outage-rfc-for-dummies/