On Jul 13, 2009, at 3:05 PM, Mel Flynn wrote:

On Monday 13 July 2009 08:36:42 John Almberg wrote:
The other day, a FreeBSD 'expert' told me that it is important to
have the DNS server for a domain on the same server as the domain's
web server. Supposedly, this saves doing tons of DNS look ups over
the network. Instead, they are done locally.

Bogus. A high-performance webserver should not be doing DNS lookups, other
then application driven ones, like verification of email domains upon
registration. If having hostnames in the live logs is mandatory by some weird company policy or the webserver does not provide a configuration setting to
turn this behavior off, then more performance is gained by having the
nameserver on the network gateway as the likeliness of cache hits and
especially negative cache hits is increased. As others have mentioned, network overhead is negligible. Human noticeable delays are caused by upstream DNS servers slowly or not at all responding when a client IP is being resolved.

Secondly, a named cache size depends on available memory. A high performance webserver uses plenty of that, so you wouldn't be able to grow the named cache to "almost caching the entire net" size, which you would be able to on a
dedicated machine.

Thanks for all the comments on this topic. Glad I put 'expert' in quotes. I had a feeling...

-- John
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