All the data centres I worked in had Halon and in recent times its replacements as fire suppression system. Unlike water, these systems suffocate the fire and once vented the equipment is undamaged. Water, computers and high electrical currents are a very bad combination.
It's not unheard of, like when the South Korean government lost a bunch of its data in a data center fire. Don't have the only copy of your data in a data center, and you won't have to worry about such a thing happening to you.