Where I work, we have to very old Alpha boxes running OpenVMS 7. They also have Multinet and are using the BIND component for DNS services. We are planning on retiring those boxes and replacing them with x86 servers running Linux. I've decided to go with Gentoo Linux for this and I've inherited two old boxes (A PIII >1GHz system and an old PIII quad Xeon 500MHz system) to do this with.
My concern is that my co-workers are adamant that the x86 systems won't be able to to keep up with the demand (we host about 70 domains in DNS) the way the Alphas did. My suspicion is that these x86 systems are just fine. However, what I really want to know is where the real utilization for DNS comes in. Is it CPU heavy? Is it RAM heavy? Or is it I/O heavy? I would suspect RAM first and CPU second based on what I've seen at home. But to be honest, in my experience DNS has been a pretty low resource service to run.
I honestly don't see our organization as being that big and 70 domains seems like a very small load even for the PIII boxes I just got. But, I'd be happy with any insight anyone here can provide.