Today in Hong Kong, I presented a look at the use of hypervisors in OpenStack. The question is, does it really matter which you choose? Like most things in technology, the answer is, “It depends.”
Back in 2010, when OpenStack was new, there were just two hypervisors: Xen, the default choice, as it was what you got if you launched a VM at Rackspace or Amazon, and KVM, the open source hypervisor that you chose if you were on the bleeding edge. By 2012, however, that had changed, and KVM had taken the lead, with Xen losing momentum. Today, more than 90 percent of the deployments we see here at Mirantis use KVM, with VMware emerging as a surprising second choice.
Of course, it’s not that simple. Xen is still around, and along with Hyper-V, has its devotees, but we are also beginning to see the rise of containers, such as LXC, Parallels, and Docker, which have their own advantages and idiosyncrasies.
And of course each has their own issues and advantages. Images tuned for a specific hypervisor may not run well on another. A number of entities are building out cross hypervisor migration tooling. KVM is becoming the default hypervisor for OpenStack, it’s easy to tune and supports the widest set of OpenStack features. ESXi doesn’t support all OpenStack features (most notably pause/unpause and resize), but overall support is good and getting better all the time. Containers are currently a somewhat fragmented space but offer low overhead and other exciting opportunities.