Should DNS be on same server as webserver?

John Almberg jalmberg at
Mon Jul 13 20:48:03 UTC 2009

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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