Software DNS hghi availability and load balancer solution

david raistrick drais at
Tue Jan 18 13:42:57 CST 2011

On Tue, 18 Jan 2011, Rhys Rhaven wrote:

> Having hit these issues myself, I heavily recommend a real frontend
> proxy like nginx or varnish.

A frontend proxy (nginx, varnish, haproxy, or anything else) doesnt give 
you HA any more than any other loadbalancer solution does.  You need a way 
to send traffic to another frontend server when the primary frontend 
server fails, or is overloaded, transparently.

The tools we have available these days to do this are VRRP-like solutions 
(which all of the appliances use) that use multicast, some amount of 
NAT and routing magic (which I've often not seen done sanely), or DNS 
solutions (better known as GSLB) that dynamicly change the DNS responses
depending on conditions (which could be source location, or could be 
server availability, or whatever).

Normally, VRRP would be the way to go.   But these days multicast isn't 
supported everywhere (major example - Amazon EC2), leaving DNS...

david raistrick
drais at   

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