HP BL460c HP BladeSystem c7000 Enclosure technologies,4th edition - Page 24

minimizes fan noise. HP recommends using at least eight fans. Using ten fans optimizes power and cooling. See the appendix for more detailed fan and server population guidelines. Scalable Operating c-Class server blades requires installing a minimum of four fans at the rear of the c7000 enclosure. Up to ten fans can be installed so that cooling capacity can scale as needs change. Using more fans allows the fans to spin slower to move the same volume of air, so each fan uses less power. Eight fans are almost always more power-efficient than four fans. As the air flow rate increases, ten fans are even more efficient (Figure 17). Slower spinning fans also create less noise. Figure 17. General relationship between the number of fans in a c7000 enclosure and the associated power draw Thermal Logic for the server blade Precise ducting on ProLiant server blades manages airflow and temperature based on the unique thermal requirements of all the critical components. The airflow is tightly ducted to ensure that no air bypasses the server blade and to obtain the most thermal work from the least amount of air. This concept allows much more flexibility in heat sink design. The heat sink design closely matches the server blade and processor architecture requirements. For example, in the HP BladeSystem BL460c server blade using Intel® Xeon® processors, HP was able to use a smaller, high-power processor heat sink than in rack-mount servers. These heat sinks have vapor chamber bases, thinner fins, and tighter fin pitch than previous designs. This creates the largest possible heat transfer surface in the smallest possible package (Figure 18). The smaller heat sink allows more space on the server blades for DIMM slots and hot-plug hard drives. 24