The venerable mainframe virtualization platform allows mainframe users to create multiple virtual partitions for a wide range of operating systems, including traditional mainframe OSes like z/OS, VSE/ESA, z/VSE, TPF, z/TPF, but also Linux.
That extra memory should make it possible to scale the number of workloads running under z/VM, said Kevin Leahy, IBM director of virtualization. "As customers scale their virtual environments, memory management always ends up being the #1 issue," he said.
Lots of Linux
That's especially important for shops running Linux, which according to Leahy, has been the "real sweet spot" for z/VM as of late.
"We see a lot of consolidation of Linux workloads on the Z platform," he said. "They started with x86 and now they need to scale it."
Marist College, a liberal arts college in Poughkeepsie, New York, runs the brunt of the college's operations on a Z9 mainframe running z/VM 5.2, including four z/OS partitions and about 600 Linux guests that are assigned to students studying computer science.
Martha McConaghy, strategic planner and project manager for the college, said that she fully expect to upgrade to z/VM 5.3 as it becomes available. "[Memory] is the main reason we keep upgrading every year. When you run as many guests as we are, we have to squeeze out as much memory as we can," she said.
But not all large z/VM shops are feeling the memory crunch -- at least not yet. Nationwide Insurance has two Z9s running z/VM 5.2 with over 400 Linux guests across four production and four test/dev LPARs, each with under 50GB of RAM, and at that level, "We're not seeing memory constraint," said Steve Womer, Nationwide senior consulting IT architect.
"We actually find that Linux in a virtualized environment runs better when you watch the memory closely -- when you don't have more memory than you actually need." To keep memory consumption in check, Nationwide monitors its memory overcommit ratio -- keeping it at 2:1 virtual-to-physical in its production environment, and 4:1 on its test and development box.
But Womer has certainly seen rampant growth of Nationwide's Linux on zVM environment. From the get-go, "we felt that this environment would have to scale extremely well," he said. In 2005, when Nationwide first set out testing Linux on z/VM, Womer predicted they'd have 100 servers by the end of the year. In fact, they ended up with 200.
"This system is scaling out much faster than we thought it would," he said
Odds and ends
Nationwide is nevertheless beta-testing z/VM 5.3, which includes several other features, among them:
- Guest support enhancements, including an IBM z/OS testing environment to simulate the virtualization of zAAP and zIIP specialty engines;
- A new Lightweight Directory Access Protocol (LDAP) server and support for IBM RACF with support for password phrases (passphrases);
- Enhanced management of Linux virtual images;
- Availability of RSCS FL530 as a priced, optional IPLA feature.
z/VM 5.3 will be generally available on June 29th.
Let us know what you think about the story; e-mail: Alex Barrett, News Director