[ Thanks to Falko
Timme for this link. ]
“Since Apache 2.1, a new module called mod_proxy_balancer is
available which lets you turn a system that has Apache installed
into a loadbalancer. This loadbalancer retrieves requested pages
from two or more backend webservers and delivers them to the user’s
computer. Users get the impression that they deal with just one
server (the loadbalancer) when in fact there are multiple systems
behind the loadbalancer that process the users’ requests. By using
a loadbalancer, you can lower the load average on your webservers.
One important feature of mod_proxy_balancer is that it can keep
track of sessions which means that a single user always deals with
the same backend webserver. Most websites are database-driven
nowadays with user logins etc., and you’d get weird results if a
user logs in on one backend webserver, and then his next request
goes to another backend webserver, meaning he’d get logged out
again. You can avoid this by using mod_proxy_balancer’s
session-awareness…”