It doesn't matter how secure your server is if it's on fire. The other Scoble has two good posts that describe the current state of the art in fire-suppression systems: here and here. This is actually something I talk about in Chapter 5 (physical &operational security), even though most of us are stuck with whatever physical plant is already in the building. Interestingly, one commenter mentioned pre-action sprinkler systems, which use water but which aren't activated without both heat and smoke alarms. (And hey, the inert suppression gas of choice is Inergen, not "Innergen".)