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If your data center is growing, or if you are trying to incorporate more processing power in the same footprint year after year, you probably know the environment of your center is heating up. Since the transition of bipolar technologies, that in many cases required water cooling, to CMOS in the early 1990’s, users have often benefited from CMOS’s maintenance free, air cooling datacom equipment. Air cooling was possible because CMOS technology was generally lower powered and generated less heat than its bipolar counterpart. But in the past decade, the performing power of CMOS technology has grown almost as fast as its popularity. CMOS technologies may now match the performance levels of bipolar. Unfortunately, this improved power may also generate increased heat. As a result, CMOS manufacturers may now be pushed to deliver improved performance technologies that can be cooled by air alone.
Data-processing and telecommunication environments designed 10-years-ago might be hard-pressed to pump enough cool air to accommodate the increased computing power. Cold aisles may be too narrow; air flow below the raised floor may become restricted by cables and piping; smaller, more powerful and hotter processors may need to work faster; and the air-conditioning (AC) units are often underpowered for the increased heat load.
Providing the floor space and AC capacity to help meet the demands of a growing infrastructure is a major challenge (See Figure 1). Many data-processing and telecommunication environments have steadily grown hotter and the trend is expected to continue into the foreseeable future. Why your current thermal control system may be inadequate.
The number of servers worldwide has increased approximately 150 times in less than a decade. During that same period, computing power per server has increased by a factor of 10. Manufacturers are forecasting a further increase to over 150W CPUs this year alone.
For many businesses the demand for processing power has greatly increased since their data center was completed. Unfortunately, while the cost of this additional processing power may have been stabilizing or even decreasing, the cost of cooling those resources generally did not. This means more powerful computers may have been introduced in the same rack space designed for much less advanced units. While these more powerful processors were being added, too often the AC equipment required to cool them was not added and probably for good reason–cost.
- Cost: Adding AC units to cool existing data center space is usually expensive.
- Cost: Remodeling or expanding a data center is probably more expensive
- Cost: New data center construction is probably most expensive of all.
As a result computer rooms may be getting warmer and warmer, while IT and facility managers struggle to determine the best and most affordable fix.
Not only are more powerful servers being introduced to data centers, but demand growth may also have forced IT managers to fully populate racks that in the past were only partially filled. Many of those racks may now hold servers with multiple processors, where before each server might have had only one or two processors. In today’s data center it is common to find racks fully populated with equipment with multiple, and more powerful processors. All of this added power may generate more heat than the data center’s current AC units can cool.
Processor cooling-power—what does and does not work
Before trying to solve the heat problem it is important to understand what is happening in your data center environment that may be adding heat.
To help dissipate heat from electrically active IT hardware, AC treated air is pumped into the floor space below the rows of server racks (See Figure 2). The chilled air enters the data center through vented tiles in the floor and fills the cold aisle in front of the rows of racks. (For non-raised floor data centers the chilled air enters through diffusers above the cold aisle. Although construction of data centers differs, the heat problem they face is similar, and the technology described here applies to both.) The built-in fans of the stored hardware pull the cool air through each rack, chilling the warm components (processors, power supplies, etc.) of the hardware. Heat is exchanged and the air becomes warm.
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