Why is choosing the right rack PDU important?

Jan. 19, 2021
Legrand's Calvin Nicholson lays out your various options in rack PDUs.
By CALVIN NICHOLSON, Legrand -- In layman's terms, a rack Power Distribution Unit (PDU) is a device that can be fitted with multiple outlets to effectively control and distribute electricity. The two main types of rack PDUs can be classified as either non-intelligent PDUs or intelligent PDUs. Creating the proper configuration for your data center will require you to first understand the key differences between these two types of rack PDUs.

Non-Intelligent Rack PDUs

There are two main types of non-intelligent rack PDUs.

1. Basic PDUs: A basic PDU is typically a power strip that accurately distributes the correct voltage and current to multiple outlets within an IT environment. The basic PDU can be used to supply power to IT equipment within racks.

2. Monitored PDUs: As its name suggests, a monitored PDU visually displays the current electric information. It is important to note that in non-intelligent rack PDU, the display information can only be viewed locally, and lack remote capabilities.

Intelligent Rack PDUs

There are four main types of intelligent rack PDUs.

1. Metered Input PDUs: This type of intelligent rack PDU displays metered power locally and over a secure network. The metering capability helps managers avoid overloading circuits. It also helps them to more easily calculate the Power Usage Effectiveness (PUE).

2. Metered Outlet PDUs: The meter power is displayed locally and over a secure network. It is used to accurately determine power usage, as well as the available capacity at the rack level. Finally, outlet-level metering can help managers efficiently identify the power consumption at the device and server level. This identification makes it easier to effectively allocate costs to specific data center customers.

3. Switched PDUs: This type of intelligent rack PDU has the same features as the Metered Outlet PDU, while simultaneously providing the control needed to power on / off switches to specific outlets. The latter capability increases remote capabilities by allowing authorized users to securely power devices on / off, create power sequencing delays that minimize the risk of inrush currents, reduce the risk of unauthorized access to devices, and reduce the data center's costs and environmental footprint by powering off devices that are not being used.

4. Switched PDUs with Outlet Metering: This type of Intelligent Rack PDU successfully combines all of the capabilities of Switched PDUs, Metered Outlet PDUs, and Metered Input PDUs. It is the most robust type of intelligent rack PDU and can be used to help data centers effectively reduce costs and maximize energy efficiencies across devices. 

Why is Choosing the Right PDU Important?

As IT buyers struggle with smaller budgets, a lower price point isn’t just a deciding factor -- it’s the deciding factor. Since basic PDUs retail for less, they may appear to be a better buy. Others may not believe that the advanced features of Intelligent Rack PDUs provide additional value, or that their organizations have the time or resources to benefit from them. As a result, many buyers choose basic PDUs despite the fact that Intelligent PDUs provide greater value and cost savings in the long term. To understand why Intelligent PDUs are the better purchase, we must first examine the common issues they can resolve.

An Intelligent Approach

In short, data centers are facing more challenges than ever before. These challenges need to be addressed in order to contain operating costs and meet new business demands. Data centers will need to make optimal use of power, space, cooling, and people. The Intelligent PDU is the platform that can address all of these issues.

1. Power Capacity Planning: By leveraging outlet level power management capabilities, users can quickly identify ghost servers and stranded capacity across the data center. Given data centers have a fixed amount of power and network resources, it’s crucial to be able to maximize them. This allows for smarter and more informed decisions about how to outfit your rack properly.

2. Power Monitoring:

Know Your Power Consumption - With the incredibly high cost of running a server, it’s important to identify rack power consumption at the inlet, outlet, and circuit breaker level. Inlet metering is crucial for determining overall server power usage and availability at the rack. Metering at the outlet can help you understand power consumption of a specific device or server, and metering at the circuit breaker provides early warnings if a circuit becomes heavily loaded and runs the risk of tripping.

Remote Power Outlets On and Off - With Intelligent Rack PDUs, you can remotely power on and off specific outlets to reboot idle servers from any location. They can also help you determine how to shift power loads and get full control of your power usage for a more efficient IT environment.

3. Environment Management: By connecting devices such as Raritan's plug-and-play SmartSensors into a rack PDU that detect environmental conditions such as temperature, humidity, airflow, air pressure, water leaks, proximity, vibration, and contact closure, you can monitor the environment around your mission critical IT assets. To maintain a safe and optimized environment, you can set thresholds and configure alerts to be aware of what is happening in your data center, even when you are not there.

4. Physical and Network Security: Intelligent PDUs with configurable firewalls, passwords, and customized SSL certificates can serve as a launching pad for extended functionality that can help protect your most important resource – data. They also support many physical securities such as combating internal threats with webcams and intelligent door locks, outside forces with firewalls, and human error with asset management tags/sensors and SecureLock™ power cords – keeping the data center secure is one of the most critical areas for all businesses.

5. Asset and Change Management: Asset Management Tags (AMTs) and Asset Management Sensors (AMSs), provide data center operators an accurate, automated, real-time inventory of all IT assets and their locations, down to the 1U level. These integrate with data center infrastructure management (DCIM) software to easily track assets, determine capacity in a number of areas, and manage adds, moves, or changes.

6. Three Phase Power: The average power consumption per server has rapidly increased with the adoption of high-power computing IT devices. Three-phase rack PDUs help support the growing demand of power-hungry IT equipment, delivering the power requirements needed to support the increase in power consumption in data centers. Three-phase PDUs also support load balancing, which is a procedure to evenly distribute the rack equipment’s current draw among the PDU’s branch circuits so more total current can be supplied with the greatest headroom in each branch circuit. This can rarely be executed perfectly, however, maintaining the power load on each phase to be within 10% of each other is a good practice. Three-phase intelligent PDUs can report on differences between phases and send alerts when the differences exceed a predetermined percentage.

7. Simplify Rack Setup and Management: Data centers need to be agile when it comes to setup and management of their complex IT hardware. Having the most flexibility in deployment and management is vital when commissioning new or existing PDUs. This ensures that they stay up and running while also being reliable and cost-effective. With recent developments in technology, Intelligent PDUs offer multiple solutions to simplify rack setup and management of hundreds or even thousands of PDUs. This not only saves you time, but it can be done with or without a network, making it incredibly convenient.

The right type of intelligent rack PDUs for your data center will enable you to reduce costs, increase energy efficiencies, lower carbon footprints, identify idle servers, and achieve a whole host of ROI-enhancing benefits.

CALVIN NICHOLSON is Senior Director of Product Management at Raritan, a brand of Legrand. He is responsible for overseeing product strategy and product management for PDUs and other related products. He holds a number of patents in both the power/data center and gaming industries and has held various positions within Server Technology Inc., including Director of Product Marketing and Director of FW Engineering. 

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