HP ProLiant DL288 HP Power Regulator for ProLiant servers - Page 15

Increasing server density and performance per watt Another way to take advantage of Power Regulator is to reduce power consumption of individual systems by using the Static Low Power mode to release power capacity for additional servers in a rack. This makes it possible to deploy more servers in a rack and thereby increase density and performance in cluster environments. Figure 10 indicates the difference in system power consumption for Static High Performance, Dynamic Power Savings, and Static Low Power modes of Power Regulator over varying loads. The same server configuration used in the previous test was used to gather this data. At 100 percent load, the system power delta is approximately 100 W less for the HP Static Low Power Mode than for the other two modes. Running a system in this mode can reduce the maximum system power consumption by 100 W. This reduction in maximum power consumption makes it possible to deploy more servers in a rack and thereby increase overall capacity or performance of clusters. In a 100 percent load scenario, a rack limited to 5 KW of power would support 14 servers running in Static High Performance mode, as shown in Table 4. By switching to Static Low Power mode and effectively limiting 350 watt servers to 250 watts peak load, rack density can be increased. According to this calculation, an additional six servers could be supported within the 5 KW limit. Table 4. Rack density calculations Peak rating with maximum no. of servers 350 watts per server 250 watts per server No. of servers supported in an 8-KW rack 14 servers 20 servers If the average server application load were less than 60 percent, then adding six more servers could potentially increase the rack performance by almost 40 percent without exceeding the maximum power rating of the rack. This assumes that the application scales linearly when more servers are added. If a server does exceed 70 percent application load, the performance of that server may be limited to less than that of a fully powered server. Based upon the example given with the DL385 G5 at 100 percent utilization, the system would use 71 percent of the power while delivering 73 percent of the performance. The ROM-based Power Regulator solution allows for the power limiting feature while still delivering higher performance per watt within a rack. Ensuring uptime Some customers over-populate a rack relative to its power rating because they assume that all the systems in a rack will not be simultaneously utilized at 100 percent of capacity. However, events can over-tax such systems and cause circuit breakers to trip and bring down all the servers in the rack. By setting some or all systems to Static Low Power mode, administrators can increase system availability by effectively limiting maximum system power consumption with minimal or no effect on non-peak system performance. 15