This table compares the features and performance of the various virtualization technologies available for Linux.  If you spot something that is not up to date, or think of something missing, feel free to update this page.

||         || full virt || paravirt || license || x86  || x86-64 || IA64 || PPC  || performance || notes ||
||         ||           ||          ||         ||      ||        ||      ||      ||             ||       ||
|| Xen     || (./)      || (./)     || GPL     || (./) || (./)   || (./) || (./) || paravirt very fast, full virt slow/medium || full virt needs VT / AMD-V, supports SMP guests ||
|| KVM     || (./)      ||          || GPL     || (./) || (./)   ||      ||      || still slow || requires VT / AMD-V, upstream ||
|| lhype   ||           || (./)     || GPL     || (./) ||        ||      ||      || slow/medium ||       ||
|| UML     ||           || (./)     || GPL     || (./) || (./)   || ??   || (./) || slow       || upstream ||
|| qemu    || (./)      ||          || GPL     || (./) || (./)   || ??   || (./) || slow/medium || runs in userspace, kQEMU not GPL ||
|| OpenVZ  ||           ||          || GPL     || (./) || (./)   || (./) || (./) || very fast   || shared kernel ||
|| VServer ||           ||          || GPL     || (./) || (./)   || (./) || (./) || very fast   || shared kernel, no performance isolation ||
|| VMware  || (./)      ||      || proprietary || (./) || (./)   ||      ||      || medium      ||        ||

Notes:
  1. Paravirtualization is fundamentally faster than full virtualization, with the exception of the userspace implementation in UML.
  1. Full virtualization performance in KVM and Xen is largely limited by the overhead of trap & emulate. Emulating multiple instructions at once at the time of a trap should bring it up to speed with VMware.
  1. OpenVZ (Virtuozo) and VServer are not virtualization technologies per se. They carve up a single system in "super chroot" jails. All the containers run on top of the same kernel.
  1. Qemu can emulate different guest architectures, eg. running an x86 virtual machine on a PPC guest.
  1. Parts of Qemu are used in the full virtualization implementations of Xen and KVM.