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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..
I leave this on: http://home-solutions.hsn.com/amana-12-000-btu-portable-air-conditioner-and-dehumidifier-with-remote_pf-450623_xp.aspx?club_id=450623&sz=888&sf=HW0130&rdr=1&cm_mmc=Shopping%20Engine-_-Froogle-_-Home%20Solutions-_-5502594&cawelaid=349282299 ... and make sure the closet door stays closed.
Depending on how your facility is ducted, it might not cost much to try both options and measure the results. Even if you have to spend a few thousand doing so, the long term savings from choosing the best method for your site would probably be well worth the cost of testing.
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.
Contain and exhaust your heated air, vent it up outside
That way it doesn't mix with the cold air much.
If you just contain your cold air, then you have a situation where the hot air is staying in the room, and that heat will be absorbed over a larger surface area, by all the things in your server room (including the Air handling units).
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.
Patent keeping the not side hot and the cold side cold.
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.
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.
When you contain the heat, you then have the ability to move it around and use it for cogeneration, thus vastly increasing your overall efficiency.
The answer will be specific to each implementation.
But in general, it should be pretty obvious to anyone that understands basic thermodynamics: get the "cold" into the servers without mixing it with the ambient or letting it touch any hot metal, and get the heat out of the servers without mixing it with the ambient or letting it heat up any other metal.
It should be pretty obvious that air is not really the best way to do this; air goes all over the place, and is not a very good thermal conductor (relatively speaking).
There are entire 10k+ machine datacenters in France that use only liquid cooling circuits, right up to the servers. Energy costs for running the external condensers are a small fraction of what it would cost to do the same thing with air. Of course, it helps if you only have your own machines in such an environment, but if APC, Emerson, etc were serious about efficient cooling then they'd partner with HP, Dell, etc. to make standardized systems that would allow this...
I mean it worked for the McDonald's McDLT back in the 80's...
'He who has to break a thing to find out what it is, has left the path of wisdom.' -- Gandalf to Saruman
It's cheaper to generate heat than cold. So I'd go for cold containment.
Actually containing both might be best since then you will have a "room temp" air gap between the two and air is a fantastic insulator. IF you do not contain the hot then the heat will diffuse and the air on the other side of the vinyl curtain will be warmer than room temp. This will warm your incoming cool air. The effect may not be particularly noticeable but it would be an interesting test to see if there is a noticeable improvement to doing both.