The Mainframe Can Help Customers Go Green

The System z platform has been answering the call of energy efficiency for decades

The System z platform has been answering the call of energy efficiency for decades
Illustration by Gina and Matt

IT facilities face major challenges regarding hotspots and power consumption. Growing computing needs and multiplying applications have forced many IT departments to add hardware, which consumes power and throws off heat, necessitating expensive cooling systems that bring their own power demands.

In contrast to this complex tangle of power and heat problems, the mainframe presents a cool and increasingly efficient alternative. "Customers report consistently that hotspots or out-of-power conditions in datacenters are caused by distributed system proliferation, not mainframes," says David F. Anderson, PE, IBM* green consultant.

Over the last 13 years of the IBM complementary metal-oxide semiconductor (CMOS) technology-based mainframes, the "big iron" computers have become more energy efficient as measured by watts-per-MIPS. The ninth-generation CMOS mainframe, the System z9* platform, is more than 30 times more efficient than the first CMOS mainframe.

The mainframe has the flexibility to help solve power and heat challenges while reducing run costs. The latest generation of mainframe computers may help datacenters stay within their current power envelope or allocation while processing more work efficiently if the potential benefits of consolidation and utilization are exploited and maximized.

Typical utilization rates on x86 servers range from 5 to 10 percent. "Analyst opinions at the Stanford Analyst Meeting in October overwhelmingly identified distributed servers as running 5 to 10 percent," says Anderson. "Some said that this was generous and that there are many servers running in low single digits." UNIX* servers perform better, averaging 5- to 20-percent utilization. A System z9 mainframe can achieve up to 100-percent utilization rates without sacrificing performance or qualities of service. The mainframe and its OSs are designed for high-utilization rates and clients typically plan and run their mainframes at or near 100-percent utilization during peak periods.

The latest generation of the System z9 function contains two new features designed to help datacenter administrators better manage, anticipate and allocate their power usage. First is a Power Estimator tool that generates power requirements based on possible mainframe configuration data. Administrators can enter potential future mainframe configurations in order to better anticipate and plan for power needs.

For datacenters facing power crises, the second tool may prove to be more useful. The new Power Monitoring display on the System z9 server lets administrators monitor how much power and cooling the mainframe is using in kW/hr as well as cooling in kBTU/hr. (Previously, many administrators estimated their power needs based on the label specification - i.e., "label power" - which is the maximum power rating for the server.) Often there's little correspondence between the theoretical maximum power needs of the mainframe and the amount of power the machine actually needs for a given configuration.

A z9 mainframe may have a label rating of 18.3 kW if fully configured, but the typical power usage is normally less than 9 kW. Since mainframes have high-utilization rates, they also have low variation in power needs compared to distributed servers, according to IBM measurements taken in August. A recently published whitepaper identifies that mainframes can process additional workloads with a small amount of additional energy, as little as two lightbulbs, or 150 watts. These two new tools enable better allocation and power planning for datacenters.

Aaron Dalton is a writer who specializes in business and technology topics. Aaron can be reached at

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