"Not only does the load balancer distribute the
requests to the two backend Apache servers, it also checks the
health of the backend servers. If one of them is down, all requests
will automatically be redirected to the remaining backend server.
In addition to that, the two load balancer nodes monitor each other
using Wackamole and Spread, and if the master fails, the slave
becomes the master, which means the users will not notice any
disruption of the service. HAProxy is session-aware, which means
you can use it with any web application that makes use of sessions
(such as forums, shopping carts, etc.)."