Root zone timeout and workarounds?

[denon]

I've been digging through the archives, usenet as well as a variety of 
other tech docs in search of the answer for my question.  I haven't come up 
with any results, but if this is a "frequently asked question", please 
don't be afraid to throw me to a url.

Here's the situation we've got:  I have a situation, where I've got the 
need for a relatively highly redundant dns system (who doesn't? :). On an 
Internet domain, as a test, I've listed 5 nameservers. One of the 
nameservers is at a remote location, and the other 4 are at various places 
within our internal network.  Due to the fact that the internal network is 
all geographically in the same area, there's a "good chance" all 4 here 
would go down at the same time. We don't presently have the facilities for 
more than one off-site, but I think it's safe to rely on just one.

The problem is this: When I take down the 4 internal nameservers (when I 
say take down, I mean ndc stop, not just drop the zone), the 5th nameserver 
outside responds just fine. However, I think most resolvers are timing out 
before it does. Shouldn't the root servers respond faster than the resolver 
times out? While the 4 are down, if you resolve something 10 times in a 
row, maybe 6 times it'll time out, and 4 times it'll resolve. (assuming you 
resolve something different from the same zone each time .. not caching/etc.).

Is this a common problem? If all 4 of the internal nameservers go down, 
will the 5th be of any use?

I'd appreciate any insight you can give me, TIA.

Best Regards.