Utterly unrelated to Knuth, and probably not useful for picking DNS servers because of their more static nature, but you might enjoy Ceph's CRUSH load distribution algorithm. Very rough gist: you can use it to e.g. set policy to avoid two replicas in the same rack, and ensure third replica goes on a different floor. And you can express server overload to migrate data off of one gradually, etc. Ceph uses that, with servers gossiping about failures & overload, to have clients directly contact the right servers.

https://ceph.io/assets/pdfs/weil-crush-sc06.pdf

(Disclaimer: Ex-employee. It's all open source.)