After searching a little bit, I wasn't able to find any specific information on this, so here I am. We've got a single 42U rack with 6 servers and some switches. It is currently housed in a coat closet with a 14,000 btu portable air conditioner (our third!). We need to move our servers into a properly configured space. One idea that has popped up is a custom built walk-in cooler. At first, I thought this might be a great idea, but then I thought about ventilation, humidity, and electrical concerns. Does anybody have any thoughts on this idea? I'm guessing that there are some really obvious reasons (that I'm missing) why this is not a good idea...
The idea was actually used for server rooms at one point in time. Today we understand that in-rack (small deployments), hot/cold isles, raise floor ventilation, and the 'newest' open-circulation designs are more efficient and have a considerably better ROI than putting your DC in a commercial size refrigerator.
I don't know what temperature range a walk-in cooler would operate at, however, your typical server room doesn't need to be all that cool. Good ventilation is important. I'd think a walk-in cooler would overkill compared to just using a portable server room AC or a dedicated unit on the roof.
Its usually recommended to keep the server room between 68-77F. Although I've heard that Google is recommending 80F.
Either way, I'd use a temperature sensor in the room to notify you of a cooling failure. Black Box makes a good one.
Here's an article that may help - http://www.datacenterknowledge.com/archives/2008/10/14/google-raise-your-data-center-temperature/
There is a particular problem with cooling gear in small spaces: airflow. If you can simply cycle a decent volume of outside air through the overall enclosure (or put the gear in a much larger overall room) then the actual amount of refrigeration required is substantially reduced.
It is a fairly common trend now to use fresh air cooling in large data centers (Intel was an early adopter in NM). Focus on moving lots of air (even if it is warm outside) through your racks and into your cold aisle and then on pulling as much air as possible out of the hot aisle. The gear will be somewhat warmer but still well within rated norms if appropriately designed. A lot of $$$ can be saved both on chillers and the electricity to run them..
Servers already have built in aircon, hence all of those fans. I use an 'ucoustic' active rack cabinet which has a typical front to back server airflow that is augmented by baffles and a couple of large fans in the rear doors that push warm air into a couple of ducts that exit through a wall vent. Very effective (don't remember the kw ratings supplied by manufacture but think around 4.5). In winter I recycle the warm air back into the office and save on heating bills.