Should DNS be on same server as webserver?

Mel Flynn mel.flynn+fbsd.questions at
Mon Jul 13 19:05:25 UTC 2009

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.


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