Google's Liquid Cooling

I wonder what the economics of water cooling really is.

Is it because chips are getting more expensive, so it is more economical to run them faster by liquid cooling them?

Or is it data center footprint is more expensive, so denser liquid cooling makes more sense?

Or is it that wiring distances (1ft = 1nanosecond) make dense computing faster and more efficient?

It's a mixture of both 2 and 3. The chips are getting hotter because they're compacting more stuff in a small space and throwing more power into them. At the same time, powering all those fans that cool the computers takes a lot of power (when you have racks and racks those small fans add up quickly) and that heat is then blown into hot isles that need to then circulate the heat to A/C units. With liquid cooling they're able to save costs due to lower electricity usage and having direct liquid to liquid cool as apposed to chip->air->AC->liquid. ServeTheHome did a write up on it last year, https://www.servethehome.com/estimating-the-power-consumptio...

I've never done DC ops, but I bet fan failure is a factor too— basically there'd be a benefit to centralizing all the cooling for N racks in 2-3 large redundant pumps rather than having each node bringing its own battalion of fans that are all going to individually fail in a bell curve centered on 30k hours of operation, with each failure knocking out the system and requiring hands-on maintenance.