Don't forget that in a parrallel rendundant system, if the fail-over switch or mechanism is any less reliable than the individual components themselves, you might as well not use a fail-over system! Of course this is all theoretical, but any failover system IMHO that uses a software mechanism *built-in* to the devices that can fail is just plain stupid. It's akin to the 'software firewall' vs hardware firewall debate -- hardware firewalls are better because they isolate the hacker from your computer and increase security! If you truly want to build a foolproof redundant failover, it should be a seperate hardware box, like a network switch that senses a fail and brings the other system online. Just from browsing this post and casual knowledge is seems there are very few systems for computers like this, or they use a software method for failover. Does anybody know of any network hardware devices that do just this? Are they efficient? Are the swtiches more reliable (have greater uptime) than the computer servers behind them?