In today's world, we are looking everywhere for power savings. In the datacenter environment, I see more and more focus on the power efficiency, yet, I also see that the servers keep on being made with focus on density. I have trouble to understand the rationale here.
My point is that in high density setup, we mostly need to have small fans with high speed for the cooling. These high speed fans have a power consumption that is way higher than what few low speed fans would have.
Example :
My company (small 15ppl office) bought a 5U server from DELL, it came with a 12cm fan with electrical properties : 12V 2.7A, that's 30+ Watts... The air was then ducted to a passive heatsink on the CPU.
I replace it by one 12cm, 12V 0.2A fan, replaced the passive heatsink by a cooler with a 12V 0.2A fan, added 2 extra such fans at the back of the drive bays.
Result : I dropped the power consumption by 60% (not accounting for the further savings thanks to PWM regulation) and temperatures are way better than before. Cherry on top, it runs silent.
My question then: Why do datacenters use high density servers? Space is cheap (most datacenters are built in countryside where land cost is neglectible and the buildings themselves can easily be built bigger), why not go for lower density, easier to cool architectue?
Or did I get it wrong in my analysis of the market?
Edit to clarify more
In other words, why do data centers choose to build 1 U servers rather than 4U servers. the latter would surely take 4 times more space, but at the end of the day, the extra cost should be limited to just extra square meters in the building. Cooling needs remain the same (as long as computing power remain the same, but because of lower density, it is way easier to achieve and could be achieved at a fraction of the power (not to mention that low density equipment is easier to maintain/repair).
