It started as underfloor. Great big CRAC. However, it died, the parts were no longer available, and getting a new CRAC in was apparently impossible. So the wallmounted units went up. We've got 12 of them, and they barely keep up. Many are blowing into the back of racks. It's a right mess. There's massive hot and cold spots. As I say tho, the room is being wound down, so there won't be much left in there soon.

That was pretty much my thought. Or other data centre is a horrible mess of cages, walls, and wall-mounted AC units. It's being slowly closed down, luckily!

If we were to retro-fit it at work, I'd say cold aisle. To do so would mean curtains at the end of the aisles, as the under-floor vent grids are in front of the racks. The CRACs are at the end of the room sucking in air through the top, so it'd be cool air pumped up through the floor, into a cold-only zone, sucked through the racks, blown out the back into the rest of the room where it just swirls about until it's pulled into the CRACs again. I reckon it could be done cheaply and quickly. Do do it with the hot aisles would require more containment to get the air back to the CRACs. I think it'd be a case of which air flow it fits best.

Yes, yes, and a thousand times yes. So much cool stuff to see at BP. Contrary to popular beleif, there's a LOT more to England than London. You'll pay through the nose in London, so take a trip out to the other towns and places, and see what you can find. Nearly every major town has a museum of some kind (the County Towns are best for this), and there's a ton of other places inbetween. Visit London by all means, but don't forget about the rest of this country.