[ Thanks to Marius Ducea for this
link. ]
“I hate to move a website to another server, but in real life
there are many situations were this will happen (maybe you need to
upgrade your current server to a better one, maybe your current
server is on a bad datacenter, or you just found a better financial
deal, or maybe you only need to change the IPs on the same server,
etc.). Besides some other problems that might appear (for example
software incompatibilities, and the site not running the same way
on the new server), the major problem you might face is the DNS
caching problem. This means that based on what your current DNS
configurations, for a period of time your site will be accessible
on both servers. Now this might be ok, but in most situations it is
not. For example you will have the emails delivered by some remote
servers to either server, or some users browsing your site still on
the old server (causing problems with e-commerce sites, or sites
that depend on the various data that is saved while users browse
the site). I have completed successfully with minimum downtime many
such moves and I will show you how this can be done with a very
simple DNS trick…”
Related Story:
EnterpriseNetworkingPlanet:
Harden BIND9 Against Cache Poisoning(Apr 12, 2005)