Re: Round robin .vs network load balancing by Anthony
Anthony
Sun Jul 27 01:55:11 CDT 2008
"r042wal" <rob@wiztalknospam.ca> wrote in message
news:uLwcX1q7IHA.2224@TK2MSFTNGP05.phx.gbl...
> What is the difference between DNS round robin and the Windows Netoek Load
> Balancing service? If I want to mirror two web servers for redundancy,
what
> do I need to set up?
>
The difference is that with DNS round robin the clients will see different
IP addresses as the DNS server dishes out the set of IPs for identically
named A records.
Whereas with load balancing the clients will see a single IP address and the
load balancer directs the traffic.
DNS round robin is not a good solution for redundancy. If one of the nodes
goes down, you first have to go and remove its A record from the DNS server
but then it may take some time before such a change is propergated. In the
meantime you may have a number of clients attempt to access the dead IP. In
a public environ it also means you need muliple public IPs which is
wasteful.
With load balancing you can remove a host from the set immediately (if it
doesn't detect an unresponsive host automatically). The only affect of a
downed server on the clients would be if some of the clients had session
data on that server. However if the intention is to build a robust solution
then you would not use server based session data (or at least not data that
couldn't be automagically reconstructed).
--
Anthony Jones - MVP ASP/ASP.NET