Slashdot Mirror
What's the Proper Temperature for a Server Room?
Izzard asks: "As a network engineer, I sometimes have to spend many hours in other people's server rooms. One in particular has a good few servers, DVD jukebox, plenty of monitors and switches etc. It's a thick, stone-walled room with a big door. It would get very, very warm were it not for the two huge air conditioning units in there. Someone has decided that these units will be set to maintain a constant air temperature of 17-18 deg. C (62-64F). After an hour or so of sitting in the air stream from these units my legs go numb and fall off and I can't type. Now my guess is that it would be fine to set the units to maintain, say, 21-22 deg. C (70-71F) to make it more comfortable for those of us who have to work in there. This argument comes up a lot, and my position is that the room doesn't need to be refrigerated, *per se*...it only needs to be prevented from overheating. Consequently I maintain that a *consistent* temperature of 'pleasant' for the room is almost as good a consistent temperature of 'a bit nippy'. Is there a definitive answer to this?"
...at the radio station I work at, the main studio containes a bunch of sensitive electronic equipment like OnAir Consoles, computers, standalone editing stations... and that room is kept 24-7 year round at a constant 71*F. Not too cold to stay in for extended periods of time, and not too hard on the AC unit, but keeps the equipment running in great condition.
I have a server room w/ over 100 2u/4u units installed, and numerous routers/switches etc. This room isn't optimal, because it has a false ceiling installed, but it does have its own A/C. We keep it at 72. Our other server room also stays at 72, but its noticably cooler in there because the ceiling is over 20 feet high. Heat rises ya know?
So, unless you have VERY sensitive equipment, or some other special reason for keeping it that cold, 72 is fine.
Nobodies Prefect
Tidbits for Techs Technology Blog
At least datacom equipements. PC and big irons may be a bit more flimsy. But, for what I know of a BIG vendor of datacom gear, all the products are specified to run from 5C to 40C and are actually tested at -5C (23F) and 55C (131F) ambient for weeks in a row. The nominal operating temperature is assumed to be 25C.
;-)
So from 17C to 40C, there's quite some room. Yet, watch out. Those temperature are specified at the cooling inlet of the equipment. With lateral cooling, the gear at the wrong end of a row of racks may suck heated air from the other racks and see much higher temperature than ambient. That's bad room design
IMHO, the guy who spec'ed 17C is overdoing it (and padding the wallet of the local utility). 25C should be OK.
SNS Not Sig
The air temperature of the room simply has to be low enough to keep the equipment heathy. With good airflow between equipment, 70 degrees F could be fine. Without proper airflow, that same temperature could create hot spots that exceed the equipments specifications, bringing on early failure.
One problem with excessive cooling is that maintaining humidity becomes difficult. Equipment in a machine room needs humidity. Humidity means more efficient transfer of heat to air, and helps to keep static electricity from become a problem.
Too cold can be as much a problem as too hot. In the early 90's, IBM had to specify *minimum* air temperature limits to keep some disk drives happy.
A.
...bringing you cynical quips since 1998
Most of the labs I've built or worked in, we've set up the ACs somewhere around 70-72 degrees. It's plenty cold while still leaving a small amount of headroom. The headroom is useful in case there's a sudden influx of heat and it takes a while to restabilize the temperature. Can't really predict what sorts of wierd things might cause that - a crapload of new equipment, an A/C unit going out of service for an hour, etc, etc..
It's very important to get your humidity correct as well. If the humidity is too low, static buildup becomes easier and static damage more frequent. If it gets too high, corrosion occurs faster. Computers like to be in the middle, if I remember right the ideal for most machines is around 35% humidity? It's been a while, that might be off by a bit.
Don't forget the whole BTUs thing. All your equipment will have a sticker or manual (or call the company) saying how many BTU of heat it puts out at max. Add them all up and make sure you have enough A/C capacity to account for the BTUs during a failure scenario (e.g. Buy 3 AC units that can handle 1/2 the desired BTU, so you have N+1 redundancy). Be sure to estimate the future as best you can in the BTU calculations - replacing A/C units when upgrading new servers in a fully loaded production room can be a bitch.
Computers like stability too, so try to set it up such that the humidity and temperature stay constant while all your gear is running. If they're wobbling up and down throughout the day or week, you need to fix it. You can buy cheap chart recorders for this, they drag a pen over a graph and show you a temperature line for a week or more. Assuming your A/C is adequate for the BTUs, the wobbling is most likely from bad airflow design.
Airflow design can be a black art, so you might want to get a professional. In general, most datacenter-class machines suck cold air from the bottom and/or front and exhaust out the top and/or back. Space out your vent tiles, too many too clsoe together can shunt air away from the inlets on your equipment. But by all means place vent tiles here and there in the empty areas to even out the room.
And if you're looking for professionals to do these kinds of things, up to and including designing and building new datacenters from scratch, I can't recommend IBM Global Services high enough. They really kick ass at these things. It almost makes up for AIX sucking so bad
11*43+456^2
Set it to where it's comfortable, keep the monitors off when you're not in there. 77 deg F.
If you want to get more complicated, monitor the inside of the boxes and just keep dropping ambient till you hit your target (of temperature inside the case).
You'll save money, keep your equipment cool, and be able to work in there comfortably.
I used to work as a HVAC tech at Wright-Patterson AFB in Ohio. As such a good portion of the equipment we maintained is for computer rooms (including a Cray system).
/kc
From the HVAC viewpoint, two important factors are the heat load vs. capacity and the design of cooling equipment.
Air conditioning units loose compressors frequently due to "slugging". Slugging is what happens when the refrigerant is not fully boiled off as it leaves the evaporator and returns to the compressor. If liquid reaches the cylinder of the compressor, the reed valves get bent (in a reciprocating compressor) rendering it useless. New "scroll" compressors can deal with this a bit better however, they too will fail in some circumstances. Simply put, the warmer the room, the more likely that all the refrigerant is boiled off before it reaches the compressor and the accumulator. With the room chilled to colder temps, the refrigerant may not boil off fully due to the small temperature differential between return air temp and discharge air temp. chances go up in the potential problems that can occur. This directly relates to the life expectancy of the compressor. While high quality air conditioning units are designed against such conditions with accumulators and suction pressure regulators, a regular air conditioner typically has no "anti-slugging" devices because they are designed to run under very specific conditions (outdoor 70-100+ and 72-82 F indoor temps. (something to keep in mind if you are thinking installing a run of the mill residential/commercial air conditioner unit in your server room to save money).
BTW, over sizing the equipment can be just as bad as under sizing. Oversize the equipment and it will short-cycle rapidly thus wearing out the mechanical and electrical components, humidity control issues, and slugging.