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Rack PDU Basics

Rack Power Distribution Units (PDUs) provide electrical power to various IT devices such as servers, networking and storage equipment. They are typically mounted in IT equipment racks.

When racks of servers first became popular in the 1990s, rack PDUs offered little more than basic power to data center equipment. As data centers evolved, however, so did power management technology. Today, IT administrators have a range of devices to choose from, each offering various levels of capability.

In the sections below, we’ve outlined the characteristics of four types of rack PDUs, using Frost and Sullivan’s classifications as a general guide.

What types of rack PDUs are there?

Basic PDUs
Basic PDUs are power strips that are constructed of high-quality components for use in critical environments such as data centers. They distribute correct voltage and current to multiple outlets.

Metered PDUs
Metered PDUs offer the features of basic PDUs, plus they measure current draw (load) at the PDU level and display the data locally. More sophisticated models also offer user-defined alarm functions and remote access to the data over a serial or network port.

Switched PDUs
Switched PDUs offer the features of metered PDUs and also provide remote on/off switching of individual outlets and load metering at the PDU level. They enable authorized users to power cycle devices securely and remotely; and they may also provide a power sequencing delay as well as some outlet use management.

Intelligent PDUs
Intelligent PDUs can be controlled remotely via a Web browser or command line interface (CLI). Definitions of what constitutes an intelligent rack PDU vary, but in general, models meter power at both the PDU and individual outlet level and provide real-time power monitoring of a variety of electrical parameters. The number and type of the electrical parameters, their accuracy and what the PDU does with the information, such as sending alerts, determines the PDU’s level of intelligence. Built-in support for sensor information, such as temperature and humidity, may also be included. Remote outlet switching is not a requirement for an intelligent PDU, since many IT operations may value detailed information but not want the ability to switch off outlets.

Types of Rack PDUs
  Basic Metered Switched Intelligent
Rack power distribution almost always almost always almost always almost always
Rack PDU level metering of current almost never almost always sometimes almost always
Remote outlet switching almost never almost never almost always almost always
Outlet level metering of current,
active power, apparent power, kWh		 almost never almost never almost never almost always
Encryption & secure access almost never almost never sometimes almost always
Directory services & user mgmt almost never almost never sometimes almost always
IP and SNMP accessibility almost never sometimes almost always almost always
Environment sensor support almost never sometimes sometimes almost always

Legend
almost never Almost Never sometimes Sometimes almost always Almost Always

For more information on the types of rack PDUs, see Raritan’s "Power Distribution Units (PDUs): Power monitoring and environmental monitoring to improve uptime and capacity planning."

Learn more about selecting the right rack PDU

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