PDU: definition
The PDU (power distribution unit) is an essential component of any network infrastructure, particularly in data centers. These power distribution units reliably distribute electricity to all equipment mounted in a rack. Given that server density is increasing and energy security is also a major issue, it is essential to understand the functions and specific features of PDUs in order to maximise the efficiency of your installations.
What is a PDU ?
Definition of a PDU
A PDU, or Power Distribution Unit, is a device specifically designed to supply power to IT equipment in server racks and cabinets, as well as network cabinets. It is the last component in the power supply chain, before the end equipment.
It includes advanced protection to compensate for electrical malfunctions and has complex monitoring features that are suitable for the most critical environments. The PDU is much more than a conventional power strip!
The primary power supply is transformed into controlled distribution to multiple devices. The PDU is not an electricity generator but transfers and distributes the energy available from the power supply in a controlled and intelligent manner. This feature helps to prevent power interruptions. It should be noted that space and performance constraints are fully taken into account by the PDU in complex IT environments.
What is the purpose of a PDU in an IT system?
A PDU distributes continuous mains power to multiple devices. A power distribution unit does not condition or generate power, but relays AC power from a generator, uninterruptible power supply (UPS) or utility power source to network equipment, servers, telecommunications equipment and other critical peripherals in a computer rack. It meets three key requirements: organised power distribution, optimal equipment protection and, finally, detailed monitoring of power consumption. Each server room houses one or more racks, which contain at least dozens of devices that require a continuous, guaranteed and protected power supply. The IT PDU plays a centralising role, as it provides concrete visibility into individual power consumption.
By separating, for example, the uninterruptible power supply circuit from the non-uninterruptible power supply circuit, it ultimately optimises overall energy management. It facilitates maintenance while improving the resilience of the installation in the event of an incident affecting a power source.
The collective intelligence of the PDU enables detailed information to be gathered and transmitted to supervisory bodies. It also ensures proactive management of energy resources. A powerful ally for optimising costs and anticipating infrastructure development needs. In our Edge data centers (UltraEdge), the PDU is regularly monitored so that it can be adapted to new demands arising from increased power densities linked to AI or IoT by extension.
Role of the PDU in rack power distribution
The PDU in a data center ensures terminal distribution from the various centralised systems. From a connection downstream of a floor PDU, electricity is distributed evenly from the grid or a backup generator in the event of a major malfunction. The hierarchical architecture ensures fully controlled power redundancy. In a rack, it is essential to optimise space utilisation, which is why side mounting at height can be used to optimise the consumption of relevant units.
Preserving preferential access to electrical connections allows for the implementation of high-density equipment. In addition, the use of metal mounting rails simplifies the installation and/or relocation of server units in server rooms, which can sometimes be confined spaces.
Compatibility with industrial connection standards facilitates integration with all types of equipment. C13, C19 sockets or specialised connectors can be adapted to the specific needs of each installation. The advantage is that this flexibility powers all types of devices, including switches, screens, NAS, routers and servers, and the PDU is customised and secure.
The main types of PDUs in data centers
PDUs are essential for efficient power distribution and reliable operations, contributing to the smooth running of data centers while preventing anomalies such as downtime or equipment failure. They are indispensable for ensuring the power supply and proper functioning of all equipment in high-demand environments.
There are several types of Power Distribution Units (PDUs), each designed to meet the specific needs of different data center configurations. Let's take a look at each of them and their main functions:
Basic PDU
Basic PDUs offer no-frills power distribution and are particularly simple. Although they lack monitoring features, basic models include standard electrical protections such as circuit breakers, an on/off switch and operating lights. This streamlined design is not recommended for critical applications; however, their high reliability and ease of implementation can be useful in less critical environments where sophisticated monitoring is not required.
The often unbeatable value for money can be effective in small installations without complex requirements, such as racks equipped with office equipment and non-critical archive servers. In addition, the fact that they do not incorporate new-generation electronic equipment optimises longevity and reduces the potential risk of failure.
Basic models generally offer between 6 and 24 sockets, depending on equipment requirements. Integrated protection includes individual or grouped circuit breakers to prevent overloads. This local protection prevents an incident on one equipment from affecting the entire rack's electrical distribution.
Smart PDU
Smart PDUs offer advanced remote monitoring and management features via network interfaces. Real-time collection of consumption, voltage-specific information, circuit intensity and separate socket data enables granular management of energy consumption resources. All in all, this facilitates cost reduction.
An SNMP (Simple Network Management Protocol) interface facilitates integration into existing supervision systems. Monitoring of electrical PDUs along with other equipment within the network is centralised and therefore easier. The advantage of automated alerting is that it anticipates any threshold exceedances and the occurrence of an electrical malfunction, allowing proactive action to be taken before a critical incident occurs.
It should be noted that this remote switching functionality, made possible by the intelligent PDU, is transforming server room operations in the long term.
Rack PDU
The rack PDU (rPDU) is designed for specific integration into standardised cabinets. It makes full use of the available space and offers high socket densities without compromising accessibility. Particularly common in data centers, vertical or horizontal mounting allows adaptation to the constraints of each installation. This optimises the internal organisation and distribution of the rack.
The easily adjustable connectors facilitate the installation of network cabling in the most confined spaces. The modular design limits the curvature of the power cables while improving air circulation in the rack. The thermal efficiency and ease of maintenance of the systems benefit directly from the optimal cabling organisation!
These rPDUs also offer monitoring modules, which are interchangeable and hot-swappable, allowing for upgrades without interruption. The equipment's lifespan is significantly extended by the scalability of the rack PDU.
Advanced features for optimised management
Energy monitoring
IT infrastructure management is made easier because advanced PDUs enable controlled consumption while optimising power factor and electrical quality with industrial precision. The data makes it possible to identify the most power-hungry equipment, and the use of each device is then optimised according to constraints, whether budgetary or environmental, for example.
Better planning for infrastructure upgrades is simplified through access to consumption history and identification of usage frequencies. This makes it possible to identify, for example, the most favourable times of day or month to perform maintenance. PDUs help load balancing and ensure proper power distribution, reducing the risk of overloads and downtime. This is crucial for maintaining availability in a data center. Optimising investments through proactive resource sizing is made effective with the highly preventive approach of IT PDUs.
In edge data centers such as UltraEdge, integration with energy billing systems facilitates very detailed cost allocation by service or application. High modularity enables the implementation of a green IT policy while raising awareness among users of the impact of energy consumption by activity or department. Highly customisable dashboards make it much easier for the various stakeholders to use these elements.
Remote management and automated alerts
Centralised management can be performed from any network entry point, provided sufficient access is available, via SNMP and web interfaces. Maximum accessibility significantly reduces physical travel for data center technicians and facilitates the most common operations such as maintenance and monitoring. Diagnostics performed by network administrators and DevOps result in ultra-responsive reactivity, reducing operating costs. Fully customisable notifications, for example, alert on-call teams during specific time slots and alert a business manager if relevant.
This ensures that the right person is always contacted. The proactive approach prevents downtime through early, planned maintenance. Automated ticketing tools create a request for each intervention, providing context and the expected information. The traceability of maintenance-related operations and operational processes is fully optimised!
Electrical protection, security and redundancy
Highly innovative electrical devices provide maximum protection against power surges, interference and electrical faults that can damage even the most sensitive equipment. Optimising the quality of the power supply effectively increases the reliability and service life of equipment in server rooms.
Power redundancy prevents a single point of failure. For example, two PDUs powered by independent power sources ensure service continuity, even if one of the power lines fails. Although common in the most complex environments such as edge data centers or IX data centers, it is important to ensure that equipment is 100% compatible with redundant power supplies.
Automatic failover optimises service continuity without the need for human intervention. In the event of a main power failure, the IT system immediately switches over to the alternative backup source. Data integrity and the maintenance of critical services or applications are carried out seamlessly and with maximum fluidity.
How to choose the right PDU for your IT rack?
To choose the right PDU, start by calculating the power consumption of your equipment, such as servers and switches. This will help you determine how much power your professional training unit and/or rack will need. Be sure to plan for future growth by choosing a PDU that can meet both your current and future needs.
It is important to choose the best type of PDU for your installation and power source:
• Single-phase PDUs are common in small data centers or home office setups and are typically used with standard voltage.
• Three-phase PDUs are more effective for larger data centers, as they can handle higher loads and are ideal for large-scale operations. Ensure that your PDU matches the type of power supply used by your data center to ensure compatibility.
Key criteria to consider
We have identified a number of key criteria to consider:
● Electrical power
As the primary sizing criterion, a standard rack can consume between 3 and 10 kW depending on the density of its equipment. A computing environment requiring maximum performance exceeds 50 kW per rack. This requires high-intensity three-phase PDUs.
● Volume and type of sockets
These determine compatibility with the equipment to be powered. C13 to C14 cables are commonly used in server rooms, while C19 cabling is more suitable for high-power equipment or even specialised connectors. This distribution between switchable and non-switchable sockets directly influences remote management, energy optimisation and improved security via the PDU.
● Management and optimisation in the PDU
These are maximised; measurement by phase, by socket or overall depending on the expected granularity. Environmental sensors are implemented for targeted measurement of temperature and humidity levels, which enhances operator supervision in the interfaces. The modularity of the interface must be continuously adapted to the tools used by the organisation..
Ensure that the PDU you choose has safety certifications such as UL, CE, or RoHS. These certifications guarantee that the PDU meets the most stringent safety standards while effectively protecting your equipment.
Comparison of options: rack PDU vs. modularity
PDU racks allow for optimal integration into standardised racks. The specific design optimises the number of available sockets while maximising accessibility. This approach is most suitable for stable environments with predictable requirements.
Modular solutions offer high scalability and are particularly adaptable. The interchangeability of socket modules, dedicated monitoring units that can be replaced at any time, and expandable features allow the equipment to evolve according to needs. This ultra-advanced flexibility comes at a higher initial cost, but hardware obsolescence is reduced and adaptability is optimal.
A redundant architecture, integrated into UltraEdge data centers, combines a multitude of PDUs to avoid single points of failure. Two PDUs powered by interdependent sources promote service continuity, even in the event of a major failure. This approach is essential for the most critical services and business applications, and justifies the higher equipment cost and mitigates the risks associated with potential downtime.
Future scalability of PDUs
Choosing a type of PDU requires that we think about scalability in an ever-expanding ecosystem, so we must choose a PDU which can grow with our future needs and our data center. Look for features such as remote control and environmental monitoring to help you optimise energy management and efficiency as needs evolve.
With the use of AI in PDUs, maintenance needs can be anticipated, preventing problems before they arise. This enables smarter power management and more efficient operation in data centers.
Deployment and monitoring with UltraEdge
The integration of PDUs into the UltraEdge ecosystem, with our ultra-dense network of 250 Edge data centers and 7 IX data centers (based in Aubervilliers, Bordeaux, Courbevoie, Lille, Rennes, Strasbourg and Vénissieux), optimises the management of distributed infrastructures.
We efficiently centralise the monitoring of power supply equipment with other equipment and components in our data centers, providing a clear and unified view of the health and availability of each installation. The high correlation between energy expenditure and application loads allows us to identify necessary optimisations and their urgency, if applicable.
Automation is a key feature of our local data centers, and we exploit the switching capabilities of smart PDUs to optimise energy consumption. These features include, for example, the automated shutdown of non-critical equipment, sequential start-up to limit current demand, and intelligent switching between power sources.
Smart orchestration of each resource reduces operational costs and improves overall efficiency. Predictive monitoring also allows for detailed analysis of consumption data and anticipation of potential maintenance or upgrade needs. Directly integrated AI agents enable proactive detection of any operational anomalies. This reduces the need for corrective action thanks to preventive maintenance. What's more, native integration with our in-house tools guarantees ultra-efficient and rapid deployment, facilitating the implementation of any new setup.