Tip

Tailoring server BIOS settings for cool servers without wasting energy

Optimizing server BIOS settings for a server's workload will help balance performance with cooling requirements.

Few servers perform at their maximum possible levels, so they should not be run on their highest performance settings. Server BIOS

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settings can control performance modes to meet the demands of a given workload. You can conserve energy and data center cooling resources by optimizing how cooling fans operate in conjunction with servers' processors and memory.

DIMM temperature throttling

IT professionals rarely think about controlling the heat associated with memory modules, but modern servers can include hundreds of gigabytes of memory spread across more than a dozen high-density dual in-line memory modules (DIMMs). Modern servers use airflow components and thermal sensors to intelligently direct memory cooling based on the system's available components.

Dynamic closed-loop thermal throttling is the most intelligent thermal-control mode; the server adjusts fan speed to regulate temperature that DIMMs sensors report. Technicians can adjust the thermal set point; if the DIMMs get warmer, the on-device temperature sensor alerts the server to increase fan speed. As DIMMs cool, the fan speed decreases.

In contrast, static closed-loop thermal throttling lacks set-point adjustability for its closed-loop system of sensors and fan control. And static open-loop thermal throttling means constant-speed cooling is applied to the memory components without temperature intelligence. By default, a server's BIOS often selects the most intelligent thermal throttling mode based on components it detects.

Fan profile characteristics

Modern servers include 10 or more adjustable-speed fans. Adjusting the fan characteristics can enhance system cooling. BIOS fan profile settings can switch the system's cooling between performance and acoustic modes.

In performance mode, a server uses fans aggressively to cool the overall system. Servers should use performance mode while processing demanding workloads, but most servers select performance mode as the default. This drives the fans harder than may be needed, and it's noisy.

Acoustic mode tells the system to first throttle back computing resources, if possible, to mitigate heat output without ramping up fans. Acoustic mode can degrade server performance, so disable it while processing critical workloads.

Additional fan settings

Server BIOS settings usually default to no fan offset, but you can tweak this. Use a fan offset to increase fan speed, addressing slightly elevated system heating issues.

More server BIOS information

NUMA, DBS and other settings

Change your BIOS password

Safeguard information with protection features

In data centers with very cool ambient air, consider quiet or idle fans. Instead of defaulting to a minimum speed, cooling fans turn off entirely at a set temperature. Infrequent bursts of fan activity keep servers cool while saving significant amounts of energy, especially when the number of fans is multiplied across dozens even hundreds of physical servers. If you're also using a fan offset, be aware that this could keep the fans running at a reduced -- but not stopped -- rate.

Default thermal settings are fine for typical deployments. But with intelligent systems onboard and IT pros who understand their options, server behavior can be tailored to balance power, performance and noise for any data center situation. As with any production server changes, adjust only one setting at a time and then test to measure the effects of any changes.

This was first published in July 2013

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