Next we add to the powered data center a Heating, Venting, and Air Conditioning (HVAC) system. Now the facility has fully conditioned space and power suitable for reliably hosting telecom equipment (Figure 12-11). This property now is much more valuable than plain real estate.
HVAC systems are critical for maintaining an operations environment for networking and computing equipment. According to IBM, computing machinery operates best between 18° C (65° F) and 29° C (85° F) with humidity between 20% and 62% relative humidity. Too much humidity can cause system failure, while too little humidity generates static electricity. IBM recommends an optimal temperature of 24° C (76° F) and 45% relative humidity.
HVAC infrastructure provides this conditioning. HVAC systems also benefit from economies of scale. Large-scale IDCs can utilize high-efficiency (and high-cost) HVAC systems and share the costs across a potentially large number of customers. These larger systems have the added benefits of requiring fewer units to perform the same task, resulting in higher Mean Time Between Failures and lower Mean Time To Repair.
Figure 12-11. Heating, Venting, and Air Conditioning ring in the data center model.