Most people know why a server room should be cold. Server room cooling is a never-ending battle. As technology continues to observe Moore's law, and both processing power and energy draw per square foot increase, it gets warmer and finds new ways to confound your server room's environmental systems. What are a server room's best practices?
However, you can't simply let your servers run at high temperatures for fear of damage. Nor can you let your server room suffer high or low humidity, which can short your equipment. While this sounds easy enough, as equipment pushes 750 watts per square foot, it isn't enough to simply crank up the air condition and expect your server room to stay cool.
The air in your server room, especially nearest the processors in your equipment, will rise to dangerous temperatures quickly if not properly cooled and circulated. You don't want your servers and rack-mounted equipment taking in the hot air exhausted from other servers, otherwise you're likely to see equipment failures, or, at the very least, inefficient server activity. Even if you had enough air conditioning units that you could keep your server room at a reasonable temperature, you would expend a costly amount of energy doing so. There are far more efficient ways to keep your server room cool.
You may know it's important to keep your server room and equipment cool, but you may not fully understand the reason why. Extreme heat and high humidity can cause major damage to your mission-critical gear. In the case of high-heat, many of the components in your equipment are only rated to operate within a specific temperature range. If your server room temperature exceeds that limit, pieces of your equipment can cease operation - or worse, fry completely, making them permanently damaged.
For humidity, it is a know fact that water and electronic equipment do not mix well. Your equipment can handle a small amount of water that is naturally in the air. But, if the humidity hits a certain percentage, your in for some trouble. If the humidity levels in your server room get too high, the water in the air can actually cause your equipment to have electrical shorts. While you may get lucky just drying it out, most of the time the water damage renders the equipment permanently damaged and it will need to be replaced. To save yourself from having to replace expensive equipment due to preventable damage, make sure your server room is appropriately monitored.
Liquid-cooled systems can help cool things down. Liquid cooled systems run chilled water or liquid coolant through coils near, on, or through your servers and racks to keep them cool. These sorts of systems are often rack-mounted closed-systems that refrigerate and recycle coolant as it passes over, under, and around your hot equipment. Of course liquid cooling is pricey and adds bulk to your server room.
Air conditioning systems in the server room are much cheaper, but simply won't do as good a job unless arranged in ways to maximize cooling potential. Air flow has to be controlled, and there has to be a way to ensure that the servers intake cold air, exhaust hot air, and that they don't exhaust their hot air into the intakes of other systems.
To deal with this problem, server room technicians and managers are looking to hot aisle strategies to help control air flow. In this strategy, servers and racks are placed in rows with their air intakes facing each other and exhaust facing away. This causes alternating hot and cold aisles. Cold air is pumped through holes in the raised floor in cold aisles. Servers take in the cold air, exhaust it into hot aisles. In the hot aisles, CRAC (computer room air conditioner) units draw in the hot return air and cool it as it's pumped back below the raise floor to re-enter the system.
Server room cooling relies on a number of different variables. These include air flow, humidity, return, and equipment distribution. That's why you'll need to monitor the effectiveness of your server room's environmental systems in many places. You must ensure that the system is working properly. You can't simply leave environmental monitoring to the environmental controls in the server room, as they're placed only at areas where cooling, air flow, and humidity are most easily controlled.
Just because everything is fine with your CRAC units doesn't necessarily mean that the cold air is being distributed to the right spots in your server room. Humidity may be fine in your return-air space, but on the server room floor, at a different temperature, you may measure something different. The varied environment of the server room demands that you spread sensors and monitoring equipment throughout your server room.
Of course, distributing sensors in the server room is no easy task. There are three major strategies to monitoring your server room:
To monitor various spots in the server room from a single device, DPS Telecom makes the TempDefender. The TempDefender is a small, rack mountable remote telemetry unit (RTU) that can handle up to 16 analog sensors reporting on all of the environmental factors in your server room. Sensors for the TempDefender may be daisy chained together, so you don't have to run a mess of cabling back to the TempDefender. You can also string sensors up to 600 feet away from the RTU, allowing you to run sensors to the most extreme spots in your server room from a centrally located device without worrying about connectivity issues.
Be careful if you measure your server room cooling system this way. Be sure to run sensors to spots likely to be hot. These include: above equipment, hot aisles, and near your hottest racks. You should also place sensors where air flow is most necessary. This can include hot air aisles on both sides of your cold aisles. This will ensure even cold-air distribution. You want to ensure that air, both cold and hot, is being effectively moved through the system. Losses and inefficiencies result in hotter server rooms and more energy expended in the cooling process - it's not as bad as a complete meltdown, but still not optimal.
If you're looking for a rack-to-rack solution, you should consider something like DPS Telecom's NetGuardian 216 G3 remote. The unit has four analog inputs, with which to measure the environment within the rack (or string sensors across a few racks) and 16 discrete alarm inputs so you can directly monitor your servers and other equipment. The NetGuardian 216 provides a total solution with which you can monitor environmental sensors and the dry contacts coming directly from your servers, so whether your problem is environmental or otherwise, you'll know about it.
Installing RTUs on every rack is the pricier solution, and, while it provides direct monitoring for your servers, which will help you ensure their safety and continued function, it doesn't necessarily tell you much about cooling systems in your server room beyond whether or not they're adequate. Measuring individual servers and racks will not likely clue you in to inefficiencies in the system.
DPS also offers a line of sensors that operate seamlessly with your RTU to give you complete environmental visibility of your server room. The D-wire sensors feature temperature, humidity and air flow measuring capabilities and up to 16 sensors can be daisy chained together. Sensors allow you to monitor your server room conditions instantaneously, so that you can fix a problem before its too late. Other sensors options include temperature sensor with a probe, non-D-Wire analog temperature and humidity sensors, smoke detectors, and exterior weather sensors.
Combining both strategies, with the TempDefender, NetGuardians and sensors, will give you the most complete view of the state of your server room. While it may seem like a large investment, you can't afford to leave your equipment vulnerable to damage.
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