With server virtualization all the rage, let's not forget it originated on the IBM mainframe--where virtualization might be a more practical option than ever for some uses.

IBM's next release of its z/VM operating system promises to let companies put more virtual machines and more memory per virtual machine on its z9 Series mainframes. That's important at Marist College, which is piling virtual machines onto its mainframes to supply computer science students with the environments they need and to run administrative workloads.

Oh, the tricks it can learn

Five years ago, the college could run a dozen Linux virtual machines on its mainframe. Today, it runs 600 of them on a z9 machine. "Students can have one virtual machine running Apache, another running MySQL, and do work with both," says Martha McConaghy, strategic planner and project manager for the college. "What IBM's done is expand the boundaries for virtualization on the mainframe."

The z9 with the 5.3 release of IBM's z/VM operating system, due by July, will be able to run virtual machines on 32 CPUs, instead of the previous maximum of 24. The z9 comes in versions with one to 54 CPUs.

Mainframes offer one increasingly important advantage over distributed servers: energy efficiency. Mainframe sales are increasing in China, India, and South America, analyst firm Butler Group says, and one reason is these machines use one-twelfth the power of distributed computing servers. IBM says its mainframe sales have increased for three consecutive quarters.

The z/VM operating system also can create a virtual machine that uses up to 128 Gbytes of memory. While McConaghy has yet to see a university or company run a virtual machine with 128 Gbytes of memory, she sees her peers at Bank of America and Nationwide constantly expanding their virtual machine workloads. IBM says its z/VM can manage up to 1,000 virtual machines on a mainframe in its labs.

If improved virtualization makes mainframes more flexible and energy efficient, count on more companies to keep their big iron humming.