Types of PDU
There are three types of PDU which include basic, metered and smart/intelligent.
Basic PDUs – simple power outlet connection and distribution
Also known as a power strip, the basic PDU is little more than a socket extension strip for mounting in a server cabinet. The PDU will have several power outlets and may include spike/electrical noise filtering and surge protection. Some basic PDUs can be upgraded with additional modules to turn them into more advanced PDUs with metering functions.Basic PDUs offer no remote monitoring and are ideal for small computer rooms and server rooms with a limited number of installed servers and IT equipment.
Metered PDUS – provide power usage information
The next level in sophistication is that of the metered PDU. Metered PDUs provide power related information that can be used to show consumption for analysis and in a colocation data center, for billing. The typical power related information monitored includes load current, kVA, kW, kWh, power factor, AC supply voltage (from a UPS system or mains power supply) and its frequency.
A metered PDU usually displays this information on a built-in display panel or GUI (graphical user interface). It may also be possible to access the information via a built-in or optional plug-in remote IP/SNMP interface. The information available from a metered PDU can be collated to check for individual PDU power consumption, as well as overall load balancing for the server rack, and overall server room and datacenter.
Metered PDUs are recommended for larger server rooms and data centers and especially those with shared resources (including electricity) which require individually billing.
Intelligent PDUs : smart energy usage and outlet controls
Intelligent or smart PDUs are the most advanced type of power distribution product with additional features to a basic and metered PDU. What makes this type of product ‘Smart’ is the extra functionality built-in. The PDUs include an IP/SNMP interface as standard and this may even be a hot-swap module to allow upgrades and swap-outs without the need for load downtime. Connection to a local IP network allows the PDU to continuous report on power consumption and provide power related metrics locally or via a web interface to a data center infrastructure management (DCIM) platform.
The advantages of continuous power monitoring even down to individual socket levels allows for instantaneous alarm reporting if safety thresholds are exceeded. Electricity consumption down to individual sockets is typically +/- 1% in accuracy allowing for timely and precision billing. Load balancing is also more precise as is the loading on upstream UPS systems allowing for redistribution of the critical power as required.
Intelligent or smart PDUs also tend to offer a wide range of additional monitoring accessories to enable them to monitor environment factors: temperature, humidity, water ingress, smoke and security.
In addition to the more advanced communications features, intelligent PDUs also tend to include switched outlets. This is an important feature as it allows individual power outlets to be remotely controlled i.e. switched off or on to assist local reboots or the powering down of individual servers. This can help to reduce the workload of data center technicians during peak periods and with sever utilization during off-peak load periods as servers can be activated or deactivated remotely.