Help Me Choose: Power Supply Unit

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.

Full Redundancy vs Fault Tolerant Redundancy
Customers often have competing priorities. Some customers prioritize performance consistency during fault conditions, while other customers prioritize higher performance and/or capability during normal operations (including getting the most out of low-line AC input). Another group may prioritize fitting in a smaller capacity PSU for cost or efficiency, and the last group prioritizes a PSU capacity with a C14 connector to avoid data center infrastructure changes (ie rack PDU).

It’s important to understand that both Full Redundancy and Fault Tolerant Redundancy will ensure the server remains operational and customer data is protected after PSU redundancy loss. But there are a few key differences to be aware of:

Full Redundancy (FR)

• Full performance during normal operation and after PSU redundancy loss.
• PSU capacity validation based on full performance power level.
• Optimized for performance consistency.

Fault Tolerant Redundancy (FTR)

• Full performance during normal operation while PSUs are redundant, but performance may be reduced after PSU redundancy loss depending on workload and environment.
• PSU capacity validation based on throttled performance power level.
• Optimized for additional performance and/or capability (ie with low line AC or C14 connector limits) during normal operation.

If the customer targets Full Redundancy, it is recommended that the Enterprise Infrastructure Planning Tool (EIPT)’s Power Supply Guide be used to determine the minimum PSU capacity.

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 (200-240Vac) input voltage. While Dell power supplies support auto-ranging, low-line (100-120V) operation may reduce overall efficiency and available capacity.

Additionally, the following PSUs require specific input voltages to deliver their rated capacity. When attached to low-line or less capable input voltage, their rated capacity can be reduced. Available capacity is limited by UL, NEC, and CE regulatory codes for the standard input connectors.

14th Generation PSUs: 1U Height x 196mm Length PSUs

Not all PSU models support all input voltages. At any given capacity point, there are a varying number of PSU models with different input voltages and connectors. Not included in this table are efficiency options or lower capacities where the capacity does not change based on input voltage.

15th Generation PSUs: 1U Height x 220mm Length PSUs

Not all PSU models support all input voltages. At any given capacity point, there are a varying number of PSU models with different input voltages and connectors. Not included in this table are efficiency options or lower capacities where the capacity does not change based on input voltage.

Please note: Not all PowerEdge servers support each PSU type. For complete PSU specifications refer to the technical specifications document for your server.

It is recommended that the Enterprise Infrastructure Planning Tool (EIPT)’s Power Supply Guide be used to determine the minimum PSU capacity.