I have a question for all you DNS gurus out there. I'd like to setup a domain so that it always goes to my main server unless that server is down, in which case it goes to my alternate server. Can I just set the site up as a virtual site on both servers and then set the nameservers on the domain like this:

NS1: ns1.mainserver.com
NS2: ns2.mainserver.com
NS3: ns1.alternateserver.com
NS4: ns2.alternateserver.com

Will this work the way I think it will? is there anything else that I'm not realizing that I should consider?

Thanks in advance for your help.

That will probably work if ns1 & ns2 are on the same server, thus they timeout and lookups move to the second set of namesevers. However BIND & the internet are not an exact science and your method probably isn't 100% effective and I wouldn't use this method in a production environment.

If you're looking for true redundant DNS services, take a look at SiteBacker by UltraDNS. http://www.ultradns.com/services/sitebacker.html