power distribution unit (PDU)

What is a power distribution unit (PDU)?

A power distribution unit (PDU) is a device for controlling electrical power in a data center. The most basic PDUs are large power strips without surge protection. They are designed to provide standard electrical outlets for data center equipment and have no monitoring or remote access capabilities. More advanced PDUs provide real-time monitoring and remote access capabilities.

PDUs manage and distribute electricity and are normally installed directly onto a rack. The power source could be alternating current (AC) or direct current (DC). It can come from an uninterruptible power supply, a utility power supplier, or a generator or other secondary power source. PDUs are also designed for power requirements that are typically much larger than home or office power strips and surge protectors.

Power distribution units ensure an organization's IT infrastructure and data center are adequately powered. Organizations also use PDUs to monitor power efficiency and uptime. Marketquest.biz estimated the global PDU market size to be nearly $1.4 billion in 2021 and predicted it will grow to over $1.6 billion by 2028.

What do PDUs do?

PDUs do essentially the same job as power strips: They supply power to multiple items at once. Data centers and other industrial environments cannot plug all their devices into one power supply. There are just too many of them. Instead, PDUs distribute power to multiple devices, including servers, computers, networking and storage devices, and telecommunications equipment.

One PDU typically can provide power for up to eight devices simultaneously. PDUs can be mounted in equipment rack enclosures to supply power to rackmountable IT equipment, such as servers, switches and routers.

These power units can also provide in-depth power management and remote monitoring. For example, data center infrastructure management equipment can take measurements of a PDU's power consumption to calculate power usage effectiveness or other statistics.

Each PDU can handle larger amounts of energy than an ordinary power strip, depending on the manufacturer and model. They typically provide power to multiple equipment racks.

What are the different types of PDUs?

Power distribution units come in rackmount, floor-mounted, cabinet and portable form factors:

• Rackmount PDUs mount directly to an equipment rack. They can control and monitor power to specific servers, switches and other data center devices and assist in balancing power loads.
• Floor-mounted PDUs provide an alternative to a facility's primary power source and data center equipment racks.
• Cabinet PDUs are units that have main and individual circuit breakers and power-monitoring electrical panels. These are used when an organization needs to provide power for multiple racks with multiple high-current
• Portable PDUs are portable, nonmounted devices meant for consumer use in homes and offices.

PDUs are also be described as basic or intelligent, with multiple types of intelligent PDUs. These include the following:

• metered inlet and outlet
• switched
• switched rack with outlet metering

Basic PDUs vs. intelligent PDUs

Power distribution units are categorized as basic or intelligent.

Basic power distribution units

Basic units only provide power distribution. The following two types are considered basic PDUs:

1. Basic PDU. This is a power strip that distributes voltage and current to multiple outlets.
2. Monitored PDU. This is a basic PDU that also displays electrical data.

Intelligent power distribution units

Intelligent PDUs provide power distribution and other features, such as power metering, monitoring, remote outlet switching, remote outlet control and notifications of potential issues. Types of intelligent PDUs include the following:

• Metered inlet PDU. These metered PDUs determine power usage and available capacity of circuits, which makes it easier for equipment provisioning. They also help in calculating efficiency metrics and avoiding overloading a circuit.
• Metered outlet PDU. Metering done at the outlet helps users in determining both power usage and rack availability. This type of PDU enables users to make comparisons to determine if a device is energy-efficient.
• Switched PDU. These PDUs have the same features as metered inlet PDUs, but they also give users control over individual outlets and groups of outlets. The outlets can power devices remotely. And switched PDUs enable users to turn off devices when not in use, saving power.

• Switched rack PDU with outlet metering. A switched rack power distribution unit has the same features as a switched PDU with outlet metering.
  
  Basic PDUs are ideal for simpler IT setups. However, an organization with a more complex environment likely needs intelligent PDUs.

Benefits of intelligent PDUs

Benefits that come with intelligent power distribution units include the following:

• Improved data center management. Intelligent PDUs include features that aid with data center management, such as metering and remote capabilities.
• Reduced energy consumption. Monitoring power consumption enables organizations to better gauge power usage. Devices can also remotely turn off outlets when not in use to save power.
• Better control over power. Remote toggle functions are available to control individual outlets.
• Energy consumption data. Intelligent PDUs can monitor energy use and provide data on where and how energy is consumed.

Choosing a PDU

Before installing a power distribution unit, an organization must decide on the type of PDU it needs. Specs to look at and questions to ask vendors and distributors when making this decision include the following:

• Where is the PDU being installed? Will it be mounted on a rack, placed on the floor or in a cabinet? Or does it need to be portable? Is it being mounted vertically or horizontally?
• What type of input power is needed? Is it AC power or DC? Is it rated for the common voltage -- 120, 240 or 330 volts -- used in the organization's country?
• How much power does the equipment need? The total power needed by equipment connecting to the PDU cannot exceed the unit's maximum load rating.
• How many outlets are needed? A PDU with more outlets than needed should be chosen in anticipation of future needs.
• What sort of plugs are needed? Some PDUs may offer a mix of outlet types to match the plugs on the various devices that connect to them.
• Are other features needed? Organizations with complex environments likely need in-depth monitoring, which requires an intelligent PDU. The specific type depends on the features an organization needs.

Installing a PDU

The specific steps involved in installing a power distribution unit may differ depending on the type of PDU. A general installation of a rackmount PDU includes the following steps:

• Align vertical-mounting brackets.
• Attach the brackets to the PDU.
• Connect the power cord.
• Route and secure the cord to its power source.
• Secure the power cord with cable straps.
• Connect the servers or rack devices to the outlets on the PDU.

Learn about how to avoid issues that may show up while setting up server racks.