Sizing a server

[John Wobus]

Any comments about good hardware/OS for running BIND9 these days?

I have the opportunity to provide input regarding server models and OS 
to use to replace our
production DNS servers.  Current load:

Queries:    800/second is typical during prime time of a typical day.
Current process size:   258M
Serves as caching server for 20,000 or so end users

Authoritative for:
around 300 zones
around 300,000 records in zone files

Currently we run on Solaris 9 Sun-Fire-V240s, 2 processors (each 1 
GHz), and the only real
issue I've seen in the life of these servers is an indication of some 
dropped packets, a problem that
went away when we increased udp_recv_hiwat.  Thus, the issue I'm most 
sensitized to at
the moment is to best assure the server will not drop packets over 
their lifetime,
which I assume will include a bit of usage growth.

Our site's "mainstream" server choices would be small Sparc Sun with 
Solaris 9 or 10,
or small IBM X-series servers with RedHat AS 4.0 (with plans to 
upgrade).  I assume that any
of these would do a reasonable job, but I'd love to hear any evidence 
to the contrary, or any
strong performance reasons to look elsewhere.

I read recently here on the bind-users list that if you use threads 
with BIND9, that 2-4 processors is
the "sweet spot".  That tidbit is welcome information (thanks!), and 
any more relevant experiences
folks have would be welcome as well.

John Wobus
Cornell CIT