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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?"
Dutch supermarkets are doing that. Test your dutch: original or test google translate: translated.
I've been in quite a few large datacenters. Some have strict rules on proper utilizing their hot and cold aisles. Some could care less.
The ones with the best ventilation have the cold air coming through the raised floor, and the hot air being pulled from the ceiling. Brilliant. Actually understanding that hot air rises. :)
Most
Some I've been in had the hot air being blown from the ceiling, and the return somewhere on a vertical wall.
At one place, they worked with us on it. We had two rows in a cage. We established the center to be the cold, and the edges to be hot. It wasn't really for temperature, it was for access. We spread the rows a little extra so we could have a couple carts and two people working at the same time. In that, we couldn't load some of the longer machines in from the "hot" side if we had wanted to. So on the aisle that we worked in, they gave us more cold air outlets, and sealed off the ones on the hot side. It worked very well. The site manager was really into making everything work as well as possible. He would walk around with a non-contact IR thermometer and spot check equipment.
Separating the hot and cold aisles with plastic would probably never work. Most racks that I've seen either are open frame, or they have a vent fan in the top. The open frame ones are obviously worthless for a plastic barrier.
Serious? Seriousness is well above my pay grade.
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.
This sorta doesn't work because what you care about in datacenter cooling is maintaining a constant equipment inlet temp. For all practical uses this means your AmbientT and ColdT are the same. What you did get right is that you want the largest delta T in your cooling equipment to provide efficient cooling. No matter what you do with hot or cold "containment" the end goal is to keep the HotT as high as possible when it hits your cooling system.
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.
Some datacenters perhaps, that don't need good Internet connectivity. But the latency between major populations and the far North makes those locations less desirable. We have struggles with the latency between Chicago and Dallas with some applications; Chicago-to-Fairbanks would be quite a bit more painful.
A recent article on Google's data centers said that they run as close to maximum temperature as possible: if the servers are rated to 90, they only cool to 88. Google is extremely efficient. The article said that the energy overhead for their data centers is only about 20%, while most data centers run 100%. Because of that, I'm sure Google has studied the server fan issue and determined that it's not a significant factor.
Put identity in the browser.