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Energy efficiency is a key server purchasing criteria. After all, the amount of electricity that a server consumes has a direct effect on the organization's data center power and cooling costs.
Addressing server energy consumption during the purchasing and maintenance process is the best way to decide what hardware is the most efficient and can help you optimize power costs.
When shopping for energy-efficient hardware, there are two energy certifications that you should look for: Energy Star and 80 Plus.
Specific hardware certifications
Make sure your new server has the Energy Star label. Servers with this label are certified to consume 30% less power than noncertified models. Certified by the Environmental Protection Agency, Energy Star criteria cover power management features, real-time power measurement and lower consumption during active and idle operations.
The 80 Plus certification does not evaluate a server's energy consumption or overall efficiency but focuses on a server's power supply unit (PSU). An 80 Plus-certified PSU must achieve at least 80% efficiency when operating at 20%, 50% and 100% of its rated load. There are six different 80 Plus certification ratings: Standard, Bronze, Silver, Gold, Platinum and Titanium.
These certification levels signify what percentage of the PSU's power levels are efficient and its specific power factor; a power factor signifies the ratio of incoming PSU power to outgoing PSU power. To achieve higher-level 80 Plus certifications, PSUs must deliver increasing levels of efficiency over time.
Tools to test server energy consumption
There are multiple devices and techniques that can evaluate -- or verify -- a server's efficiency. Enterprise-grade uninterruptable power supplies (UPSes) often have a meter that tells how much power any connected devices consume. The key to using these meters is to know what metrics they are reporting and how you can use the metrics to track server energy consumption and configure hardware accordingly. Common metrics include battery health and runtime, as well as input and output voltage.
You should confirm if any metrics require conversion to effectively manage power consumption. Many connected devices convey power consumption with amps. If you must know how many watts of power a device uses, then multiply the number of amps used by the number of volts that the device is designed to consume. This tells you how many watts the server needs to support the connected device.
Admins can also use the Server Efficiency Rating Tool (SERT) suite from Standard Performance Evaluation Corporation to test server energy consumption. This tool uses standardized benchmarking techniques to calculate various server and workload efficiency scores that can quantify a server's energy efficiency. The SERT suite tests processors, memory, storage and applications at various load levels and then provides machine-ready and admin-readable data.
An external power meter, such as the Kill A Watt meter from P3 International, is a hardware-based option. When using a meter to monitor power consumption, track power use for at least a week. Short-term monitoring can be inaccurate because power usage often fluctuates in response to workload spikes and maintenance tasks.
Online calculators can help you to determine server energy consumption without counting each individual server or connected device. Rack Solutions offers one such calculator. This calculator helps you determine how much power is consumed at the rack level and the number of watts per square foot. This information is useful when building a new data center or adding new hardware to an existing data center.
For additional help during power consumption planning, hardware vendors provide power consumption data for their products through fact sheets and configuration tools. Tripp Lite has a load calculator that can simplify the estimation process. This calculator provides power consumption data for a wide variety of servers. With this information, you can confirm that your UPS hardware can effectively support any server or connected device hardware.
A vendor's power consumption metrics may not always account for specific configurations or modifications. Installing components such as hard drives or video cards increases a server's power requirements beyond a vendor's baseline numbers. There is, however, an independent online calculator that can help you estimate how much power a server will consume based on its hardware specifications.
There are plenty of resources available for assessing a server's energy efficiency. Regardless of which methods you choose, be sure to enable the OS' power management features. Without this management function, you circumvent any server energy-saving capabilities or reporting features.