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Understanding Server Power Supplies: A Quick and Easy Guide

Posted by Integrity Global on Mar 12th 2019

Understanding Server Power Supplies: A Quick and Easy Guide

How to Choose the Right Power Supply for Your Server

When it comes to assembling a server for your organization, there are a lot of variables to consider. One of the many parts that you’ll need to include as part of your server system is a power supply. But understanding the differences between power supplies can be complicated: there are titanium, platinum, and gold power supplies, different wattages, redundant power supplies...the list goes on. Trying to make sense of it all can be a challenge.

Below, we’ve spelled out some of the key things you’ll need to understand in order to choose the right power supply for your server system. Keep reading to learn more.

Finding the Power Supply You Need

If you’re looking for a power supply for your Dell or HPE server system, there are online tools that you can use in order to find a power supply that’s compatible with the particular type of server you have. For those with HPE servers, there’s the HPE Power Advisor service. If you’re running a Dell server system, Dell offers its own online resource.

Still, though, it’s helpful to understand what differentiates one power supply from another when making your choice.

Server Power Supply Efficiency

Generally speaking, the more efficient a power supply is, the less energy you’ll use overall. If you’re running multiple servers together in a rack, the savings in electricity costs can really add up over the course of a year.

Titanium power supplies are the most efficient option, offering 96% power efficiency. Platinum power supplies are slightly less efficient at 94%. Gold power supplies offer a lower efficiency of 92%.

Essentially, the efficiency of a power supply is calculated in terms of how much AC (or, in some cases, DC) input power is needed in order to produce a given amount of output power. For example, a power supply which requires 200 watts of input power in order to produce 180 watts of output power would be rated at an efficiency of 90% (180/200 = 0.9).

The 20-watt difference between the input and output is lost in the form of heat. Aside from the added expense of the electricity involved in generating this wasted energy, another downside of inefficient power supplies is the fact that this heat has to be accounted for: you’ll need cooling equipment to remove it.

Of course, the efficiency of a power supply isn’t linear or flat when it comes to the supply’s output range. Most power supplies operate at their maximum efficiency when they’re running in the upper ranges of their rate capacity. This means that an 800-watt power supply providing 400 watts of power (50% capacity) will be less efficient than a 500-watt power supply providing that same 400 watts of output power (80% capacity).

Why does this matter? When choosing a power supply, efficiency is an important consideration -- but you have to take into account more than just the efficiency rating of the power supply itself. By accurately estimating the power consumption of your server system, you can choose a power supply that’s correctly sized and will run at optimal efficiency.

In the case of large (enterprise-level) data centers, cumulative energy losses from multiple servers running inefficient power supply configurations can be significant. To get the most accurate measurement possible, it’s often helpful to pre-configure and measure your actual system under load. However, this method can be impractical for many customers as it involved purchasing, configuring, and operating each component of the server system. As a result, smaller customers without the ability to perform such tests can sometimes end up with a power supply that exceeds their wattage needs.

Redundant Power Supplies

Redundant power supplies are used as a backup in the event of failure of the primary supply. Having redundant power supplies in place is essential for ensuring your ability to continue to operate in the event of a failure of the primary power supply.

When it comes to redundant power supplies, every server operates differently. Some will use the primary power supply for 100% of power needs until it fails, at which point they will switch over to the secondary supply. Others will balance their energy needs between the two. It’s also generally possible to configure how you want the server to make use of the two power supplies.

Server Performance and Power Supply Efficiency

On the one hand, a power supply’s efficiency rating is helpful for getting a sense of how it will perform. At the same time, though, the particular server that a power supply is used with can have an impact on its efficiency.

As this case study demonstrates, the same power supply can operate at a different efficiency in two different servers. This particular case study shows the Dell PowerEdge R720 server as performing more efficiently than the HP ProLiant DL380p, but this will obviously vary from case to case.

How Much Will it Cost to Run My Server?

It’s important to take into account both the noise level and cost of running a particular power supply.

This helpful chart compares both the cost and noise level generated by various servers for particular power supplies.

To calculate the costs for powering your particular server, there’s a simple formula you can use. Multiply the watts times the hours used (per day, month, or year, depending on what you prefer to calculate), and divide this number by 1,000. Then, multiply the result by your cost of electricity per kilowatt hour. The result will give you an estimate of your total cost to run that power supply.

Get Help with Choosing the Right Power Supply

Still not sure what power supply you need for your server system? Integrity Global Solutions stocks a wide range of used and refurbished power supplies from Dell, HP, and other leading brands. Our customer service team can help you choose the right power supply to meet your needs. Chat with us now for immediate assistance!