hardware and OS requirements

[Dan Fulbright]

Can anyone point me in the right direction to find some discussion about 
hardware and OS requirements for variuos BIND setups?  I am going to be 
setting up a DNS server for about 10,000 to 20,000 domains, and would like 
some idea of what kind of machine(s) I would need.  My instinct is to use 
Linux, but I would be open to others (mainly BSD-based).  I need to know 
things like, how much RAM and hard drive space, and, if I use Linux, what 
file system types, etc.

Thanks.