Help Me Choose: Power Supply Unit

The power supply unit (PSU) meets a critical function in a server. The power supply takes the utility power voltage for that region and converts it into low-voltage power that is required in order to run the system. Selecting the right wattage PSU will have a big impact on the overall efficiency of a server.

In order to select the proper power supply unit (PSU) for your needs, you’ll want to factor in several variables that could influence your final decision

• Determining the desired PSU rating for required efficiency
• Deciding between redundant or non-redundant power supplies
• Deciding between of high-line or low-line operation

Selecting the right size/rating

We find that customers sometimes choose the PSU with the highest power rating due to lack of knowledge on how to choose the right size PSU, fear of choosing one with a rating too small for a given configuration, or attempting to plan ahead in case the server configuration changes in the future. Choosing a PSU that is larger than needed for the actual workload may cause wasted energy consumption. When this is aggregated across an entire rack or data center, that waste can be substantial.

Dell EMC encourages customers to carefully select a power supply based on the configuration and workload of the specific IT deployment, to help realize energy savings and greater return on investment. For detailed information, please use the Enterprise Infrastructure Planning Tool at www.dell.com/calc

Redundant PSUs vs. Non-redundant PSU

In order to prevent a server from shutting down due to a power supply failure, many PowerEdge servers offer an option for redundant power supplies. These are recommended for any production environment, particularly for mission-critical environments. Without a redundant power supply, in the event of PSU failure, the server can be rendered unusable until a replacement is provided and the system can be restarted.

Dell’s entry-level offering provides a basic, non-redundant PSU. In most Dell servers, you have the option to pair the PSUs for redundancy.

High-line vs. low-line operation

In the Americas and other regions using similar electrical wiring practices, power delivered at 100-120VAC is known as low-line input power, and power delivered at 200-240VAC is known as high-line input power. Dell EMC power supplies are optimized to run with high-line (200-240V) input voltage. While Dell power supplies support auto-ranging, low-line (100-120V) operation may reduce overall efficiency.

Additionally, the following PSUs require high-line input voltage to deliver their rated capacity. When attached to low-line input voltage, their rated capacity can be reduced by as much as 50%.

Please note: Not all PowerEdge servers support each PSU type.