HP DL370 HP Power Advisor utility: a tool for estimating power requirements fo - Page 15

Figure 13 shows a rack configuration of twenty HP DL380 G6 servers receiving power through redundant power buses. This example is based on the Power Advisor calculations indicated in Figures 11 and 12. The power supplies (PS A and PS B) of each server connect through PDUs to the separate power buses. With both power buses active, the power supplies and PDUs evenly share the server load (approximately 13.8 A per bus). While a 24-amp PDU could handle the load during normal conditions, a PDU would need to distribute 27.6 amps required by all the servers if one bus should fail. For this reason, a PDU on a redundant power bus should never provide more than 50 percent of its rated capacity in normal operation. In the example shown in Figure 13, the 40-amp PDUs are required and provide headroom for additional equipment upgrades. Figure 13. 42U rack configuration of HP ProLiant DL380 G6 servers with redundant power buses Physical Configuration 40A PDU DL380 G6 servers 1 thru 10 Functional Block Diagram PS A PS B DL380 G6 servers 1 thru 10 PS A PS B 40A PDU 27.6 A DL380 G6 servers 11 thru 20 13.8 A DL380 G6 servers 11 thru 20 13.8 A Bus A (208 VAC) Normal operation Bus B (208 VAC) Redundant operation (Bus A failure) The Power Advisor indicates that the cooling requirement for the rack configuration shown in Figure 13 would be 17887.2 BTUs/hr (894.36 x 20). This level of BTU generation may require special cooling considerations such as controlled air, forced air, or chilled-water systems. NOTE For more information on power distribution strategies and threephase power refer to the white paper "Power Basics for IT Professionals" at http://h20000.www2.hp.com/bc/docs/support/SupportManual/ c01234421/c01234421.pdf 15