"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 heartbeat, and if the master fails, the slave becomes the
master, which means the users will not notice any disruption of the
service. Perlbal is session-aware, which means you can use it with
any web application that makes use of sessions (such as forums,
shopping carts, etc.)."
