The focus for IT and data center managers over the last decade has been on decreasing PUE, increasing the temperature of IT spaces, and defining new approaches to cooling in-rack equipment. However, challenges persist as power consumption within rack environments continues to accelerate.
Based on recent conversations with IT and data center managers, it’s clear they expect power consumption to creep higher, with 12 kW to 17 kW being the new normal range in many enterprise IT racks.
Space and Power
In most cases, a smaller footprint equates to a better return for IT managers, especially when deploying equipment in colocation data centers, by reducing the space required (and the associated costs) and utilizing fewer racks. Now, the ability to run three-phase power to these environments can achieve higher operating efficiencies.
The market is seeing a significant push toward 230/400 V for global data center and colocation installations (240/415 V in the U.S.) to take advantage of these efficiencies. While there are benefits gained from operating at higher voltages, they also bring along their own set of considerations.
Power-Hungry Deployments
Two primary types of deployments are driving power consumption higher and making improved efficiency essential. Each requires a different approach for specifying rack power distribution units (PDUs).
The first, 1U server deployments, fully occupy the maximum size enclosure of choice at the site (e.g., 42U to 54U enclosures). This presents the first requirement, which is outlet density per PDU or, in simpler terms, the number of outlets available per rack PDU. To fully support this type of deployment, an IT manager needs a high-power, high-outlet density PDU.
The second deployment consists of multiple pieces of high capacity network equipment, such as the Cisco® Nexus series switches or larger blade servers, in a single rack. With space at a premium, consolidation is critical for these larger chassis. One or two per rack is no longer cost-effective. As these devices can pull 1,000 W per power supply (with several power supplies per chassis), stacking three to four in the same rack can quickly push power consumption to 17 kW and beyond.
Distribution Needs for High-Power Applications
Each of these scenarios carries a specific set of power distribution needs. Recommendations for meeting these needs are highlighted in the following scenarios.
Scenario 1: High power, high outlet density
Selecting a PDU with the outlet count density to provide 42 to 54 outlets in a single power strip can allow data center managers to install A/B redundant rack PDUs into one side of the rear cabinet. Four standard PDUs are required to provide the number of outlets needed, but high-power, high-outlet-density PDUs can handle the outlet count in just two units, saving money and space. Streamlining the deployment with high-power, high-outlet-density PDUs also simplifies the incoming power into the rack, reducing four cable and conduit runs to two.
Scenario 2: High power, low outlet density
Selecting a PDU with high power input and low outlet densities for high-capacity networking and blade server equipment is critical to powering them effectively. Since the power supply draw on these units is higher, providing power from a rack PDU with a lower outlet-to-circuit-breaker ratio avoids the potential of breaker trips due to overloading the outlet group. To illustrate, a standard PDU typically has six to eight outlets assigned to an individual breaker, where a high-power PDU has one to four outlets per breaker. In high-power, low-outlet-density PDUs, the available power per outlet is higher to support an installation of the latest generation of high-capacity network equipment.
Additional Considerations and Opportunities
Going beyond outlet density, other factors, such as universal input and cabling, should be considered in high-power environments.
Universal input — While powering the equipment itself is important in these types of applications, there are some additional factors to consider. The intent of standardization to simplify purchasing, installation, and support becomes complicated by the variation in power systems that exists. New buildouts might be across different regions, having different power inputs (Delta versus Wye). Universal input connections are an option to address this. Universal input connections on rack PDUs account for differences in site input power when deploying multiple or global sites. They allow the selection of input cables to match site-specific outlet and power requirements. Standardization can be achieved using universal input so that a single PDU chassis or style can be deployed in virtually every location. While the universal capability is certainly beneficial, there are tradeoffs in added cost for the connector and cable and potential costs for global certifications.
Cabling — Cabling is critical in high-power applications where there is an abundance of opportunity for organization, color-coding, and improved reliability. Start by separating networking and power cabling on opposite sides of the rack for easier rack access and airflow. Focusing specifically on the power cabling in these dense environments is paramount. Failing to do so can result in heat problems, premature equipment failure, and downtime. Implementing colored cabling to match A/B redundant rack PDU deployments allows for easier navigation when in-rack and quick identification when a problem strikes. Finally, consider a locking-type cable solution, such as P-lok, to provide a more secure solution for cable-dense environments. The lock protects against the chance of an accidental disconnect via vibration or human error.
Higher Power Is Here To Stay
Regardless of the application, the request for more power over the years has continued to climb, and it does not appear to be leveling off any time soon. Selecting the right power equipment to effectively manage this increase will improve cost, efficiency, and reliability. While high-power racks may make up only a portion of data center applications today, understanding the challenges that arise in these environments and knowing the techniques to properly address them will be a key competency in the future.
