[Tiksi]

Usually the fire suppression is halon-like gas systems (can't use halon anymore), sprinklers are an absolute worst case last resort.

But yeah, there's plenty of

  NO CARDBOARD ON THE DC FLOOR
  NO CARDBOARD ON THE DC FLOOR
  NO CARDBOARD ON THE DC FLOOR

At every multi-tentant dc.

[skuhn]

I have only seen dry-pipe water systems lately, since halon is long gone.

I did see one system that used HI-FOG sprinklers. Smaller water droplets are supposedly able to extinguish a fire with significantly less water. You're still sad, but maybe you can salvage more equipment.

[Tiksi]

I've seen a few chem agent and inert gas systems, but only when someone realized cost of equipment + loss from downtime > cost fire suppression system, which is less often than it should be.

dry pipe systems are probably the most common though.