Slashdot Mirror
Hot Aisle Or Cold Aisle For Containment?
1sockchuck writes "Separating the hot and cold air in a data center is one of the keys to improving energy efficiency. But containment systems don't have to be fancy or expensive, as Google showed in a presentation Thursday, which discussed the use of clear vinyl curtains in isolating hot and cold aisles. Containment systems have been in use at least since 2004, but there's an ongoing debate about whether it is best to contain the hot aisle or cold aisle. Leading vendors are split as well, as APC advances hot aisle containment while Emerson/Liebert champions a cold aisle approach. What say Slashdot readers? Do you use containment in your data center? If so, do you contain the hot aisle or cold aisle?"
I thought this article was about supermarkets, where it might be a good idea anyway too..
What say Slashdot readers? Do you use containment in your data center? If so, do you contain the hot aisle or cold aisle?
I think that I speak for most readers here when I say that it's pretty much all cold aisle down here in my mom's dank basement. Not much containment either, other than some pegboard partitions.
We only resort to using containment when the servers have been very, very naughty. We've found that chains, steel cable and duct tape are the best ways to keep servers in their racks.
If "disco" means "I learn" in Latin, does "discothèque" mean "I learn technology"?
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.
Maybe I'm missing something obvious, but the answer shouldn't be complex. Base the decision to contain either hot or cold aisles on the differences to ambient temperature. If (HotT - AmbientT) > (AmbientT - ColdT), then contain the hot aisles. If it's the other way around, contain the cold aisles. This minimizes the entropy loss due to temperature mixing in the data center, I believe. Just my 2 cents.
sigfault (core dumped)
The best solution is going to based on the average ambient temperature of your location. If you're in a hot environment, why contain the cold if you need additional A/C in the datacenter for employees? Reduce costs by using the same equipment to cool both. If you're in a cold region, then let the heat also warm the datacenter. If you're in an ideal temperature environment, then you don't have much to worry about beside good air flow.
Well, as most companies that have to build a new datacenter will tell you. It's cheaper to generate heat than cold. So I'd go for cold containment. Generally speaking most companies do AIM to put their new datacenters as close to the north pole as possible simply because it's cheaper to use outside air that's natually cold. That puts countries like Canada, Greenland, Denmark, Norway, Sweden and Finland in high demand for datacenters (end technicians to staff them). If the US didn't have rediculous data laws, Alska might also be ideal.
In our new datacenter we're even using the excess heating from the servers to heat the offices ontop of the giant basements below. This sort of setup is ideal for outside temperatures that generally range below the normal cooling needs of a server (or several). But in any event there's still a huge bill to pay for moving the air back and forth, so containment is definately still an issue, as is the size of the pipes when you have say... 10MW of electricity going into your servers and quite a lot of that energy coming back out as heat ;)
--- To err is human... Am I more human than most ?
Why is this modded offtopic? OP was clearly stating expressing his support for hot aisles.
I can honestly say you win either way. The electricity/cost savings of containment will pay for itself regardless of where you put the doors. That said, whether you choose to go HAC or CAC is really choosing between different trade-offs.
HAC (The APC method): Seemed to be cheaper and easier to install. Since the hot aisle is being contained, if something happens to your coolers, you have a longer ride-through time as there's a much larger volume of cold air to draw from. However, at least when I got out of the business, HAC *required* the use of in-row cooling, and with APC, that meant water in your rows. Europeans don't seem to mind that, but Americans do (which provided an opening for Emerson's XD phase-change systems, dunno if APC has an equivalent or not yet). I personally wouldn't be too keen on having to spend more than a few minutes inside that hot aisle, either.
CAC (The Emerson method): Seemed to be more expensive, especially in refit scenarios (they appeared to be more focused on winning the big "green-field" jobs more than upgrading old sites), but it can usually leverage existing CRAC units, so you could potentially save enough there to make it competitive, as well as avoid vendor lock-in. The whole room becomes the equivalent of a hot aisle, but convection and the building's HVAC can somewhat mitigate that, so it'll still be uncomfortable working behind a rack, it doesn't feel quite the sauna that an HAC system does. Depending on whose CRAC equipment you buy (or already have), EC plug fans and VSD-driven blowers can save even more money if properly configured.
Other: I've seen the "Tower of Cool" or "chimney" style system, and flat out hate it. They look like a great idea on the face of it: much cheaper, faster installation, able to use building HVAC, etc. But let's be honest. Your servers are designed for front-to-rear airflow. So are the SANs, NASs, TBUs, rack UPSs, and practically everything else you've put in your datacenter, apart from those screwball Cisco routers that have a side-to-side pattern (Seriously... what WERE they thinking on that one???). Why would you then try to establish an upwards-pointed airflow that's got a giant suction hose at the center of the rack's roof, where it can just as easily pull cold air from the front (starving your systems) as it does hot air from the back?
Personally, I like cold aisle better. If I'm going to be spending two hours sitting behind a server because I can't do something via remote (forced into untangling the network cable rat's nest, perhaps), I like the idea of being merely uncomfortable and a bit sweaty than dripping buckets while cursing the bean-counters who forced me to lay off the PFY two months ago. There are also some neat controllers that work with CRAC units to establish just the right amount of airflow to fully feed the row and manage their output, so if running five CRACs at 50% is more power efficient than running three at 100%, that's what they do. I know folks who like hot aisle better. It's more fun for them to show-off their prize datacenter since all the areas you'd want to see (unless you're the one responsible for power strips or cable management) are cool.
I suspect that one of these choices is incorrect. Correct.
You forgot Iceland...
Yeah well, they're having a little trouble with containment right now themselves. And it appears geothermal isn't as clean as it was made out to be.
For justice, we must go to Don Corleone