LinuxVirt:

This table compares the features and performance of the various virtualization technologies available for Linux. Hopefully this table also explains why many Linux distributions today ship Xen, even though UML and KVM are upstream and lhype is getting pretty close to inclusion into the upstream kernel.

For an explanation of the technologies, please see the [:TechOverview:technology overview] page.

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

architectures

performance

SMP guests

CPU / memory hotplug

standalone host

notes

Xen

(./)

(./)

GPL

i686, x86-64, IA64, PPC

paravirt very fast, full virt slow/medium

(./)

(./)

(./)

full virt needs VT / AMD-V

KVM

(./)

(./)

GPL

i686, x86-64

paravirt very fast, full virt very fast

full virt needs VT / AMD-V

lguest

(./)

GPL

i686

slow/medium

rhype

(./)

GPL

i686, x86-64, PPC

fast

(?)

(./)

research project

MoL

(./)

GPL

PPC

fast

32 bit only

UML

(./)

GPL

i686, x86-64, PPC

slow

upstream

L4Linux

(./)

GPL

i686, ARM

medium

(./)

qemu

(./)

GPL

i686, x86-64, IA64, PPC

slow/medium

runs in userspace, kQEMU not GPL

OpenVZ

GPL

i686, x86-64, IA64, PPC

very fast

(./)

shared kernel

VServer

GPL

i686, x86-64, IA64, PPC

very fast

shared kernel, no performance isolation

VMware

(./)

proprietary

i686, x86-64

medium

(./)

LPAR

(./)

proprietary

s390

native

(./)

(./)

z/VM

(./)

(./)

proprietary

s390

very fast

(./)

(./)

typically runs under LPAR

PHYP

(./)

proprietary

PPC

fast

(./)

(./)

(./)

used on all modern IBM System p

lv1

(./)

proprietary

PPC

fast

(./)

(./)

used on Sony PS3

BEAT

(./)

proprietary

PPC

fast

(?)

(./)

used on Toshiba CellEB

Notes:

  1. Paravirtualization is fundamentally faster than full virtualization, with the exception of the userspace implementation in UML.
  2. Performance can vary wildly depending on workload. This page assumes system call intensive applications, since "fair weather" performance numbers are not very useful.
  3. Memory and CPU hotplug is mostly useful because it allows one to run more virtual machines on a system simultaneously, adjusting the amount of memory allocated to each guest depending on load.
  4. For an overview of the other benefits of paravirtualization, see ParavirtBenefits.

  5. 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.

  6. 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.
  7. OpenVZ (Virtuozo) can change memory and CPU quota during runtime, there is no real hotplug since there are no guest kernels.
  8. Qemu can emulate different guest architectures, eg. running an x86 virtual machine on a PPC guest. Qemu also has the distinction of being the only full virtualization technology that can run without root privileges.
  9. Parts of Qemu are used in the full virtualization implementations of Xen and KVM.
  10. The standalone host column indicates whether or not the hypervisor (or host OS, in the case of VM) is booted before Linux. See the [:HypervisorVsLinuxBased:comparison of hypervisor based vs. Linux based virtualization] for the debate on whether or not this is an advantage.

LinuxVirt: TechComparison (last edited 2007-01-13 20:29:57 by JeffSchroeder)