Operating Systems

• IBM is an active member and supporter of the Open Virtualization Alliance. Now this is just a good business decision. IBM recognizes there are many virtualization choices out there. However, sometimes when IBM embraces an idea, the company takes it to the extreme.
• After a hiatus of 18 months, the number of fixes and enhancements to the Linux kernel pertaining to System z’s implementation of KVM has increased significantly. This indicates real investment by IBM in the technology.
• KVM, ESX, Hyper-V, and Virtual Box are featured prominently in trade publications and journals aimed at the C-level executive. IBM also runs the openKVM Twitter feed.

This evidence reveals that KVM has increased in importance. KVM is a great technology with tremendous potential, and it’s open source. There are lessons that z/VM can learn from the vast community of KVM users. The hope is that KVM is another arrow in the quiver for System z and not the precursor to another onslaught on VM.

The bits and pieces are all there to allow a Linux system to use KVM as a hypervisor to manage a farm of virtual servers. One of the nice things about KVM is that we now get to peer under the covers to see how Start Interpretive Execution (SIE) works in z/Architecture (see Figure 7). However, to expect that the function and stability z/VM has acquired over 45 years of effort can be replaced in just a few years is dangerous thinking. There’s more to z/VM than just a hypervisor. It’s an ecosystem of tools, techniques, instrumentation, utilities, people, practices, and infrastructure that’s essential to the proper operation of large-scale server farms or cloud provisioning. What constitutes “enterprise ready” is different for an enterprise of 10 servers than one running hundreds.

Integration of or closer cooperation between KVM and z/VM is a worthy goal. The oVirt project appears an ideal mechanism for establishing a common management base to serve different sorts of virtualization technologies (see ZDNet’s “IBM's Open Virtualization Alliance, oVirt and KVM Update” and oVirt: “The Virtual Datacenter Management Platform”: http://ovirt.org).

This is all just speculation, but the history of VM is one of exhilarating highs and numbing lows. Vigilance by its community has proved vital to VM’s longevity and relevance. There’s only so much “doing more with less” that a team can take, and continuing to put the squeeze on z/VM would prove to be shortsighted and a return to the mistakes of the past.

Whatever lies ahead, there are a few immutable truths:

• The teams of developers behind VM and its Linux counterparts have great dedication and skill.
• The VM community is passionate and unwilling to ever go quietly into the night.
• There’s still a lot of fun to be had riding this rollercoaster.


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