HP ProLiant BL660c HP BladeSystem c-Class architecture - Page 20

Dynamic Power Saver Mode Most power supplies operate inefficiently when lightly loaded and more efficiently when heavily loaded. When enabled, Dynamic Power Savings mode will save power by running the required power supplies at a higher rate of utilization and putting unneeded power supplies in a standby mode. When power demand increases, the standby power supplies instantaneously deliver the required extra power. As a result, the enclosure can operate at optimum efficiency, with no impact on redundancy. Both efficiency and redundancy are possible because the power supplies are consolidated and shared across the enclosure. Active Cool fans Quite often, small form-factor servers such as blade or 1U servers use very small fans designed to provide localized cooling in specific areas. Because such fans generate fairly low flow (in cubic feet per minute, or CFM) at medium back pressure, a single server often requires multiple fans to ensure adequate cooling. Therefore, when many server blades, each with several fans, are housed together in an enclosure, there is a trade-off between powering the fans and cooling the server blades. While this type of fan has proven to scale well in the BladeSystem p-Class, HP believed that a new design could better balance the trade-off between power and cooling. A second solution for cooling is to use larger, blower-style fans that can provide cooling across an entire enclosure. Such fans are good at generating CFM, but typically also require higher power input, produce more noise, and must be designed for the highest load in an enclosure. Because these large fans cool an entire enclosure, failure of a single fan can leave the enclosure at risk of overheating before the fan is replaced. With these two opposing solutions in mind, HP solved these problems by designing the Active Cool fan and by aggregating the fans to provide redundant cooling across the entire enclosure. The Active Cool fans are controlled by the Onboard Administrator so that cooling capacity can be ramped up or down based on the needs of the entire system. Along with optimizing airflow, this control algorithm allows the c-Class BladeSystem to optimize acoustic levels and power consumption. Because of the mechanical design and the control algorithm, Active Cool fans deliver better performance-at least three times better than the next best fan in the server industry. As a result of the Active Cool fan design, the c-Class enclosures support full-featured servers that are 60 percent more dense than traditional rack-mount servers. Moreover, the Active Cool fans consume only 50 percent of the power typically required and use 30 percent less airflow. By aggregating the cooling capabilities of a few, high-performance fans, HP was able to reduce the overhead of having many, localized fans for each server blade, thereby simplifying and reducing the cost of the entire architecture. PARSEC architecture Each c-Class enclosure uses PARSEC (parallel, redundant, scalable, enclosure-based cooling) architecture. In this context, parallel means that fresh, cool air flows over all the server blades (in front of enclosure) and all the interconnect modules (in the back of the enclosure). Fresh air is pulled into the interconnect bays through a dedicated side slot in the front of the enclosure. Ducts move the air from the front to the rear of the enclosure, where it is then pulled into the interconnect modules and the central plenum, and then exhausted out the rear of the system. Each power supply module has its own fan, optimized for the airflow characteristics of the power supplies. Because the power supplies and facility power connections are in a separate region of the enclosure, the fans can provide fresh, cool air and clear exhaust paths for the power supply modules without interfering with the airflow path of the server blades and interconnect modules. 20