I thought these data centers have a way to pump in a gas that prevents fires? Remember touring a data center at some point that has this ability.
That's how the server room at my school worked. They said to get out of there if the alarm went off because the room would fill with some inert gas and you'd suffocate.
They stopped using it many places because the risk to people was greater than the equipment.
The gas is used first, then water as a fallback. I'm not sure if sprinklers are required by code in all data centers, but they would be in an office building setup like Jane Street's.