Slashdot Mirror
The Risks and Rewards of Warmer Data Centers
1sockchuck writes "The risks and rewards of raising the temperature in the data center were debated last week in several new studies based on real-world testing in Silicon Valley facilities. The verdict: companies can indeed save big money on power costs by running warmer. Cisco Systems expects to save $2 million a year by raising the temperature in its San Jose research labs. But nudge the thermostat too high, and the energy savings can evaporate in a flurry of server fan activity. The new studies added some practical guidance on a trend that has become a hot topic as companies focus on rising power bills in the data center."
No they didn't - what they did do is figure out that increased temperature is not correlated to higher failure rates - the failure rates don't magically decrease as it gets hotter.
Here's the link for your review: http://hardware.slashdot.org/story/07/02/18/0420247/Google-Releases-Paper-on-Disk-Reliability
Sadly, in an effort to save money, we hired some developers with little to no experience, and zero credentials. Turns out the program they wrote to control the thermostat eats up so many compute cycles that it visibly raises temperature of whatever machine its running on. So we ran it in the server room, because thats where temperature is most important. However by the time it would adjust the temperature the room would raise 1 Degree. Then it would have to redo its analysis and adjustments.
Long story short, the building burned down and I'm now unemployed.
It is true that if you are producing X BTUs of heat inside the room, then to maintain temperature, you have to pump that much heat out. However, the efficiency of this heat transfer depends on the temperature difference between the inside and the outside. To the extent you want to force air (or any other heat transfer medium) that is already colder than outside to dump energy into air (or other medium) that is warmer, that will cost you energy.
Also, too cold, and you will invite condensation. In your hypothetical scenario, you'd need to run some pretty powerful air conditioning to prevent condensation from forming everywhere.
For starters, people sweat and computers do not. So, airflow helps cool people by increasing evaporation, in addition to direct thermal transfer. Even when you think you aren't sweating, your skin is still moist and evaporative cooling still works.
Unless someone invents a CPU swamp cooler, that's just not happening on a computer. You do need airflow to keep the hot air from remaining close to the hot component (this can be convection or forced), but you don't get that extra... let's call it "wind chill" effect that humans feel.
I'm less concerned with the fine-tuning of the environment for servers than I am with getting the basics right. How many bad server room implementations have you seen?
I'm sitting in one. We used to have a half-dozen built-for-the-purpose Liebert units scattered around the periphery of the room. The space was properly designed and the hardware maintained whatever temp and humidity we chose to set. They were expensive to run and maintain but they did their job and did it right.
About seven years ago, the bean-counting powers-that-be pronounced them "too expensive" and had them ripped out. The replacement central system pumps cold air under the raised floor from one central point. Theoretically, it could work. In practice, it was too humid in here the first day.
And the first week, month, and year. We complained. We did simple things to demonstate to upper management and building management that it was too humid in here, things like storing a box of envelopes in the middle of the room for a week and showing management that they had sealed themselves due to excessive humidity.
We were, in every case, rebuffed.
A few weeks ago, a contractor working on phone lines under the floor complained about the mold. *HE* got listened to. Preliminary studies show both penicillin (relatively harmless) and black (not so harmless) mold in high concentrations. Lift a floor tile near the air input and there's a nice thick coat of fluffy, fuzzy mold on everything. There's mold behind the sheetrock that sometimes bleeds through when the walls sweat. They brought in dehumidifiers that are pulling more than 30 gallons of water out of the air every day. The incoming air, depending on who's doing the measuring, is at 75% to 90% humidity. According to the first independent tester who came in, "Essentially, it's raining" under our floor at the intake.
And the areas where condensation is *supposed* to happen and drain away? Those areas are bone dry.
IOW, our whole system was designed and installed without our input and over our objections by idiots who had no idea what they were doing.
So, my fellow server room denizens, please keep this in mind - When people (especially management types) show up with studies that support the view that the way the environment is controlled in your server room can be altered to save money, be afraid. Be very afraid. It doesn't matter how good the basic research is or how artfully it could be employed to save money without causing problems, by the time the PHBs get ahold of it, it'll be perverted into an excuse to totally screw things up.
If there is a failure of AC ... that is, either Air Conditioning OR Alternating Current, you can see a rapid rise in temperature. With all the systems powered off, the latent heat inside the equipment, which is much higher than the room temperature, emerges and raises the room temperature rapidly. And if the equipment is still powered (via UPS when the power fails), the rise is much faster.
In a large data center I once worked at, with 8 mainframes and 1800 servers, power to the entire building failed after several ups and downs in the first minute. The power company was able to tell us within 20 minutes that it looked like a "several hours" outage. We didn't have the UPS capacity for that long, so we started a massive shutdown. Fortunately it was all automated and the last servers finished their current jobs and powered off in another 20 minutes. In that 40 minutes, the server room, normally kept around 17C, was up to a whopping 33C. And even with everything powered off, it peaked at 38C after another 20 minutes. If it weren't so dark in there I think some people would have been starting a sauna.
We had about 40 hard drive failures and 12 power supply failures coming back up that evening. And one of the mainframes had some issues.
now we need to go OSS in diesel cars