z/VM’s ancestry dates back to the ’60s, although most sites today understand it purely as a facilitator of Linux virtualization—and for good reason.
z/VM’s career began with hypervisor technology that first appeared commercially in the early ’70s as VM/370, which allowed for guest operating systems to access services from a simulated machine created by the underlying operating system control program. The hypervisor literally ran on “bare metal,” supporting a variety of operating systems at one level removed from the hardware. z/VM was the first, and is still the favored approach, to allow multiple system images of diverse operating systems to function on a System z.
However, there are many other z/VM capabilities sites can exploit to their advantage that both complement and extend beyond virtualization. This article discusses how z/VM is making a difference for organizations—and what sites can do to get the most out of it.
The Current z/VM Market
IBM acknowledges that the ability to run virtual Linux servers captures the lion’s share of interest in z/VM these days. Forty percent of VSE customers also run production workloads in the z/VM environment, and practically 100 percent of TPF clients run z/VM for development and test support. “Approximately eight percent of z/OS clients also run test and development environments on z/VM,” says Reed Mullen of IBM System z Strategy and Technology. “They’re finding a savings in sharing system resources among multiple copies of z/OS running on z/VM in a single Logical Partition (LPAR). Developers and testers appreciate having their own copy of z/OS. They can test their environment on their schedule, without worrying about the impact their work may have on other users.” According to Velocity Software CEO, Barton Robinson, there also are pockets of sites that have built up libraries of custom applications in z/VM that aren’t vendor-dependent.
IBM’s Mullen says it’s hard to categorize all the benefits of z/VM because its options and uses are so broad.
“One reason z/VM is valuable to enterprises is because of its hypervisor technology,” Mullen says. “z/VM doesn’t constrain customers from using whatever System z technology they wish to use, and it literally frees them from some of the limitations a non-virtualized environment might impose. In a virtual machine environment, it’s possible to configure systems with assets that might not exist in the real hardware configuration. This allows clients to optimize their workloads and to experiment, innovate, and perform system performance assessments. In this way, sites can try out ideas in the virtual world before implementing them in production.”
Certainly, z/VM use is growing with the introduction of Linux. “The market had significantly dropped during the ’90s as IBM was sending out signals that the product was being killed off,” says Marist College’s Martha McConaghy. “But the introduction of Linux stopped that decline … I’ve consistently seen new faces at SHARE and other conferences and have heard anecdotal stories of new IBM customers who are purchasing hardware and z/VM in order to run Linux.”
Flexibility With Operating Systems and Facilities
With the focus on Linux, other mission- critical operating systems such as TPF (now known as z/TPF) aren’t often talked about—nor is the fact that TPF clients would struggle to support their production workloads without the z/VM layer providing cost-effective development and test support.