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IBM Releases PowerKVM Hypervisor for POWER8 Systems

open source powerkvm

In June 2014, IBM released the PowerKVM hypervisor for POWER8* scale-out systems. KVM, which stands for Kernel-based Virtual Machine, is an industry-standard hypervisor that has gained significant popularity in the open-source space. Like other hypervisors, KVM enables the sharing of real compute, memory and I/O resources through server virtualization.

According to the OpenStack User Survey conducted in November 2014, KVM has 87 percent of the OpenStack cloud marketplace ( When PowerKVM was released, the Ubuntu distribution of Linux* was also released for Power Systems*. Ubuntu enjoys 64 percent of the OpenStack cloud market, according to the same survey, and has 54 percent of the Amazon Cloud space ( The two releases provide a great one-two punch for using Linux on Power* in the cloud. While the KVM hypervisor has 87 percent of the hypervisor market share in the cloud, Ubuntu is the leading OS for cloud-based solutions with 64 percent of the market share.

The Platform Decision

IT implementation decisions have always centered on the platform; however, the definition of platform has seen a number of iterations. Figure 1 shows a typical stack of software components.

The requirements of the application to be implemented used to drive the decision and dictate the remaining portions of the stack. Over time, though, the same applications have become available across multiple OSs, which have become available across multiple hypervisors such that the platform decision is driven down to the hardware architecture. Because of this, Power Systems architecture is the clear winner. Support of PowerKVM means those shops that have implemented applications on KVM on hardware other than Power now have the option of implementing on Power with the only change being the hardware platform itself.

Design and Implementation

With that background, let’s examine the features of the KVM hypervisor. KVM provides additional capability for existing Linux distributions. KVM takes advantage of the modular design of Linux to deliver virtualization via a kernel module (kvm.ko) that adds core virtualization and hypervisor features to the Linux kernel. In addition to the kernel module, a user-space program called QEmu provides emulation (not used in PowerKVM) as well as virtual devices and control mechanisms. Rounding out the virtualization functionality is a library interface called libvirt, which uses a standard library to manage virtual machines (VMs). Those three pieces (kvm.ko, QEmu, libvirt) take a Linux kernel and turn it into a hypervisor. Rather than replacing existing functionality, such as scheduler and memory management, KVM uses the existing Linux facilities so the KVM developers can concentrate on hypervisor and virtualization functionality while other open-source developers can concentrate on their areas of specialty.

In the KVM space, VMs exist as user-space processes and are referred to as guests while the Linux kernel with the KVM module is referred to as the host.

Erwin Earley is an advisory software engineer for IBM assigned to the POWER AIX/Virtualization Delivery practice in Rochester, Minn.



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