Round Robin question

[Thomas Duterme]

Hi everyone,

I'm thinking of using  round robin DNS to act as my load
balancer for my apache/jserv site.  Here's the basic
situation:

In the past, I've only had to run one large
webserver...there was stable traffic and the one server
could handle the job.  Bursts of traffic are soon to be
expected, and therefore, I'd like to do load balancing.
Unfortunately, I don't have the money to buy fancy load
balancing hardware.  So, I'd like to do accomplish this by
using RR DNS.

I've never done this before and would like to ask a few
questions:

a) I know I will have to play around with an appropriate
ttl, but can anyone suggest something useful.   I've seen
some sites with DNS lookup times as low as 5 seconds...this
seems a bit ridiculous, but I guess is mainly dependent on
need.  I estimate to have about 500K users per day coming to
the site.

b) I'm a bit worried about bandwidth consumption.  It
appears that running low ttl DNS on a highly requested site
(500K users per day to the website) could really hammer the
DNS servers and eat up bandwidth.  How can I calculate this
bandwidth cost?

c) Are there any other issues I need to think about before
implementing RR DNS?  Can anyone share their experiences?

Many thanks in advance,
Thomas