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

Better Computing Through Virtualization

Virtualization can increase efficiency and reduce heat and power demands in the datacenter. And according to Anderson, the System z9 mainframe is the king and queen of virtualization.

Anderson explains, "Virtualization and LPAR technology originated on the mainframe. Mainframe virtualization is mature and offers the treasures needed for today's computing to be secure, scalable, robust and non-disruptive."

Mainframe rules virtualization in another sense by exploiting the z/VM* OS, the gold standard for virtualization. Thanks to a process of continuous refinement over 40 years, z/VM scales and manages virtualization of processors, memory and I/O better than any other server OS or bolt-on virtualization product. It can virtualize hundreds or thousands of Linux servers - the limit is just under 100,000 instances - more efficiently and effectively than any other virtualization technology.

Indeed z/VM has at least a 4:1 advantage over VMware in virtualization improvement, according to many IBM TCO studies authored by Scott Barille. Where VMware is an add-on or bolt-on tool, sapping performance with overhead, z/VM is actually integrated directly with the mainframe hardware.

The bottom line is virtualization can enable datacenters to run applications with fewer physical resources and thereby require less power and cooling. Virtualization lets you do more work with fewer power-consuming servers or appliances, which also need to be cooled. The mainframe has a virtualization advantage thanks to shared-everything architecture. "Shared-everything allows you to share processors, memory and I/O and waste nothing," says Anderson. IBM mainframes have been built this way for 40 years.

How the Mainframe Keeps Its Cool

Today's high-end System z9 Enterprise Class (z9 EC) employs a sixth-generation closed-loop liquid cooling system. The system contains an environmentally friendly refrigerant called R134A - the same chemical used in a car's air-conditioning system. The liquid-assisted cooling of critical technological components enables greater efficiency than could be achieved by a system that was air-cooled with only high volumes of air forces through the datacenter and machine at high velocities.

Not all mainframes require hybrid cooling. The System z9 Business Class (z9 BC) mainframe has fewer processors and runs at a slower cycle time. Therefore, it generates less heat and can maintain an acceptable temperature with just an air-based cooling system (see Figure 3).

IBM has also reduced the datacenter cooling requirements with the System z9 platform by making other improvements (see Figure 4). "A dual-core processor chip on the (System) z9 uses approximately 75 watts, the same amount of energy as an ordinary incandescent light bulb," notes Anderson, citing a Jan./Feb. 2007 IBM Journal of Research and Development article. "A multichip module (MCM) in the System z9 EC uses only 825 watts and contains up to eight dual-core processor chips, a clock chip, four L2 cache chips, two memory-storage control chips and an L2 cache controller - each of which uses only 825 watts. A hair dryer uses more electricity than MCM."

How can IBM achieve such efficiency? The mainframe design team has been focused from the earliest generations of the CMOS on achieving low-energy, high-performance design. As competitors focused on fast-cycle times, IBM strove for throughput. Therefore, the mainframe is ahead of the game with a design that's highly optimized for running many workloads at high-utilization rates with reduced cooling requirements.

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

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