Building a Two-Node Linux Cluster with Heartbeat
Commercial products from Red Hat, TurboLinux and PolyServe use the same concept of IP aliasing. When the primary server goes down, the backup server will pick up the same aliasing IP so that high availability can be achieved.
The cluster product from PolyServe is very sophisticated. It has support on SAN (server area network) and is capable of more than two nodes. It is very easy to install and easy to configure. I successfully configured the trial version without reading any documentation through a windows monitoring client. However, sophistication comes with a price tag, and the software costs more than a thousand dollars for a two-node cluster. The 30-day trial version cluster will stop after two hours, and it is not much fun for testing.
The cluster product from TurboLinux needs some fine-tuning. The installation documentation is confusing (or maybe they simply don't want people to do-it-themselves). The web configuration tool is unstable; the cgi script will crash whenever the user clicks the reload or refresh button. And of course, as a commercial product, it comes with a high price tag.
Linux is very stable and reliable, and it is quite common to have our servers up and running for a few hundred days at a time. Heartbeat works fine in my tests, and if you are looking for a product with higher availability for a small business or education institution, Heartbeat is definitely a perfect option.