If rack power consumption could be easily estimated and remained constant, there would be no need for on-going monitoring. However, server workload and rack configuration changes cause power consumption to fluctuate over time and have the potential to overload the circuit, causing equipment to shut down.
Power consumption in a server rack is not constant. In fact, it can more than double when servers are performing processor- or disk-intensive operations such as copying files. Power consumption can also vary by as much as 20% in servers running Windows Server, which automatically reduces the frequency of the server’s processors to save power when the machine is under low load. Variations in the performance characteristics of servers makes it difficult for network engineers to estimate power requirements for a server rack and ensure that an overload condition does not occur.
To ensure that rack power consumption never exceeds the capacity of the circuit (protected mains, in-rack UPS or branch PDU), a network engineer could design-in a large margin of error but this would greatly increase both capital and on-going costs. A better solution is to continuously measure the power consumption of each rack in real time using a PDU capable of remote monitoring.
A Monitored PDU supports real-time local and remote monitoring of the power consumed by connected equipment. With optional accessories, temperature, humidity, and rack security can also be monitored. If power consumption exceeds a user-configured threshold, an email or similar alert warns network engineers of potential overload conditions.