I just wanted to post a quick follow-up on the raised floor discussion. An article over at SearchDatacenter.com prompted me to do so. APC's CTO Neil Rasmussen states the following at the close of their interview:
The floor is the problem. I can make an air conditioner any size I want, but the problem is getting the air through the tiles. If I try to moving 25kW of air through tile, it's going to be 120 mph coming through floor tile. It's also very inefficient to push all that air over a distance. It takes a tremendous amount of horsepower to move it around. It's not uncommon to find just the fan taking more power than the servers in data centers.
He goes on to comment that the APC strategy is to get the cooling closer to the cabinet. When you are in a small "computer room" I suppose I can see this. When you have hundreds and hundreds of cabinets, this just seems like their way to make even more money on the deal. I am by no means an expert, but I believe their are plenty of cooling solutions that work (even for a 25 kW cabinet) that don't require cooling at the cabinet level.