Advanced Computing in the Age of AI | Wednesday, August 17, 2022

Know What Your Server Costs 

With data centers beginning to exhaust their electrical capacity, it’s becoming increasingly important for organizations to know the total cost of ownership for these data centers. By estimating server consumption and knowing the resulting business expenses, organizations will extend the life of a data center and save money and electricity.

With data centers beginning to exhaust their electrical capacity, it’s becoming increasingly important for organizations to know the total cost of ownership for these data centers. By estimating server consumption and knowing the resulting business expenses, organizations will extend the life of a data center and save money and electricity.

To estimate a server’s electric consumption, the amount of electricity each server consumes needs to be known. While a server may be rated at 1725 Watts, that doesn’t mean the server consumes exactly 1725 W of electricity. That 1725 W number is known as the server’s nameplate rating, which doesn’t say how much electricity is consumed, but instead what the power supply’s capacity is. Using solely the nameplate rating will result in an overestimation of electric consumption, consuming resources that would be better off spent elsewhere.

Unfortunately, average electric use measurements can be hard to come by, since servers tend to have variations in configuration. If a server has been around since 2005, the vendor’s power numbers will have the typical power calculations. If the server was made before 2005, the site planning documentation should have the information.

A server’s electrical cost can be variable. If a particular server is unplugged and the workload is deployed elsewhere in the data center, $333 will be saved in server electrical expense every year.

When looking at things from a data center facilities perspective, a server’s consumption is considered to be the kW used by systems at the power supply input. This is known as the IT load, which is one of three major electrical cost categories. The other categories are distribution, which measures the kW of losses from conversion of voltage and rectification, and mechanical, which is the kW of thermal dissipation equipment removing the heat generated by both the IT load and distribution.

Reductions in both IT load and distribution are considered to be hard dollar savings, meaning they’re both tangible savings that aren’t realized from not spending. Whenever a server is unplugged, the watts it would normally consume are saved, and because those watts aren’t distributed, those monetary expenses are saved.

Since only some of the mechanical load is variable, calculating the cooling cost that corresponds to server load is a soft saving, meaning the only money saved is when it isn’t spent. The soft saving varies by data center, but a reasonable portion of a facility’s wattage should be 25%.

Once all of this information is in hand, the annual operating expense of a server can be determined by multiplying the IT load cost, distribution kW and mechanical kW. Finding the savings if that server were decommissioned involves multiplying the IT load cost and the distribution kW by the total of the mechanical kW and the variable portion.

Knowing how much electricity your servers use, what is required to distribute that voltage and remove the heat generated is, as they say in “G.I. Joe,” only half the battle. Taking this knowledge to figure out what a server costs annually will not only help data centers save money, but it will also help the environment by saving electricity.

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