What are my options for a free hypervisor?
Sander van Vugt: The open-source virtualization market features two free hypervisor options: Xen and KVM. Both options are Linux hypervisors, but they approach virtualization in different manners.
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The former is a virtual machine (VM) monitor for x86-compatible computers. Using paravirtualization, Xen allows the hypervisor and the VM to communicate with one another. Today, Xen is still included in some important Linux distributions, such as Oracle's Unbreakable and SUSE Linux Enterprise Server, but has taken a backseat to other hypervisors, including Kernel-based Virtual Machine (KVM).
Xen includes several built-in management tools and supports numerous host and guest environments, as well as hardware architectures, making it more mature than KVM. The latter, however, is embedded in the Linux kernel, which some people argue enables easier management of VMs and Linux updates.
Red Hat Inc., the leading vendor on the Linux market, pushes KVM heavily. The vendor has developed a complete management platform around it, based on the oVirt standard.
In addition to Xen and KVM, you could consider usingLinux Containers (LXC) as a free hypervisor alternative. This option lets you run multiple Linux instances on one Linux kernel by allowing a host to run virtual containers on top of the host kernel. LXC conserves resources and saves IT shops money, but is not as flexible as a hypervisor. It would be a good choice for hosting providers that want to run multiple VMs in an easy, resource-efficient way.
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