Most configurations are valid. However, cooling cannot be predicted for some configurations such as when racks are not arranged in alternating cold and hot aisles. In this case, no CI value or color is shown for any rack in the immediate vicinity of the invalid configuration. For valid clusters, the actual CI value shown and associated color is based on the larger of the two hot and cold aisle CI metrics for the rack. The CI color coding is related to the cooler supply and maximum target temperature as shown in the figure below.
This color coding ensures better airflow management is enforced as the difference between cooler supply and maximum target temperatures approach zero. For example, if the cooler supply temperature and maximum target temperature are both 20°C then ΔT=0 and CI must be 100% for a rack to achieve a "green" rating. If the cooler supply temperature is much lower than the maximum target temperature, there is a large "operating margin" and more tolerance for less ideal airflow management.
Capture Index (CI) color