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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