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Unraid Freenas Comparison Essay

unRAID is also "not RAID". It's its own solution, that sort of acts like a subset of what real RAID provides but falls critically short while providing a false sense of security. Most unRAID advocates have never dealt with a real hard drive failure, or haven't been able to connect the dots of the silent corruption they occasionally experience being connected to unRAID being a really poor solution. The remainder of unRAID advocates are too scared to use something serious like FreeNAS/ZFS.

There's really no comparison when you really dig into it. ZFS is the "real deal", and is a whole separate filesystem built by Sun Microsystems around the concept of redundancy across multiple disks. FreeNAS is a front-end for FreeBSD, which is arguably one of the most solid, mature and stable OSes out there, especially when it comes to servers. Which is what you're building here.

The biggest hurdles with FreeNAS that scare people to give up and just go with unRAID are:

1) The learning curve to build the computer and set up the software.
2) Less flexibility in configuring the array (adding disks, etc).

The rewards for overcoming 1 & 2 are huge, though. It's the difference between taking a Powerwheels jeep on a safari, and getting a great deal on a new Land Rover.

My server (35W idle, silent):

Software: PMS 1.10.1.4602 running in a jail on FreeNAS 9.10.2
Motherboard: ASRock E3C226D2I Mini-ITX Server Motherboard
CPU: Intel Xeon E3-1271 v3 Quad-Core 3.6GHz 8MB LGA1150 (Passmark: 10204)
CPU cooler: Thermalright TRUE Spirit 120M(BW) Rev.A
RAM: Crucial 16GB kit (8GBx2) DDR3 PC3-12800 Unbuffered ECC 1.35V CT2KIT102472BD160B
HDDs: 6x WD Red NAS 3TB IntelliPower 64MB Cache SATA 6.0Gb/s 3.5" WD30EFRX (RAIDZ2)
Power Supply: SeaSonic Platinum Series SS-400FL2 Active PFC F3 400W ATX12V Fanless 80 PLUS Platinum Certified
Case: Fractal Design Node 304 (8.27"x9.84"x14.72")






Platform virtualization software, specifically emulators and hypervisors, are software packages that emulate the whole physical computer machine, often providing multiple virtual machines on one physical platform. The table below compares basic information about platform virtualization hypervisors.

General[edit]

NameCreatorHost CPUGuest CPUHost OSGuest OSLicense
bhyveFreeBSDx86-64x86, x86-64FreeBSD, IllumosFreeBSD, FreeNAS, pfSense, OpenBSD, Linux, Windows, Illumos[1]BSD
BochsKevin J. LawtonAnyx86, x86-64Windows, Linux, FreeBSD, Unix/X11, Mac OS 9, macOS, BeOS, MorphOS, OS/2[2][3]Windows, Linux, DOS, BSD, OS/2, HaikuLGPL
Containers, or ZonesSun Microsystemsx86, x86-64, SPARC (portable: not tied to hardware)Same as hostSolaris 10, Solaris 11, OpenSolaris 2009.06, illumos distributionsSolaris (8, 9, 10, 11), illumos, Linux (BrandZ)CDDL
Cooperative Linux (coLinux)Dan Aloni, other developersx86Same as hostWindows 2000, XP, 2003, VistaLinuxGPL version 2
CHARONStromasysx86, x86-64PDP-11, VAX, Alpha, HP3000, SparcWindows, LinuxVMS, OpenVMS, Tru64 UNIX, MPE/iX, RSX-11, RT11, RSTS, Solaris, SunOSProprietary
DenaliUniversity of Washingtonx86x86DenaliIlwaco, NetBSDNot distributed
DOSBoxPeter Veenstra, Sjoerd with communityAnyx86Linux, Windows, classic Mac OS, macOS, BeOS, FreeBSD, NetBSD, OpenBSD, Solaris, QNX, IRIX, MorphOS, AmigaOS, Maemo, SymbianInternally emulated DOS shell; classic PC booter games, unofficially Windows 1.0 to 98GPL
DOSEMUCommunity projectx86, x86-64x86LinuxDOSGPL version 2
FreeBSD JailFreeBSDAny running FreeBSDSame as hostFreeBSDFreeBSD, Linux ABIBSD
GNOME BoxesGNOMEUnix-likeUnix-likeLGPLv2
GXemulAnders GavareAnyARM, MIPS, Motorola 88000, PowerPC, SuperHUnix-likeNetBSD, OpenBSD, Linux, Ultrix, SpriteBSD
HerculesRoger BowlerAnyz/ArchitectureWindows, FreeBSD, NetBSD, Linux, macOSLinux on z Systems, z/OS, z/VM, z/VSE, OS/360, DOS/360, DOS/VS, MVS, VM/370, TSS/370QPL
Hyper-V (2008)Microsoftx86-64 with Intel VT-x or AMD-Vx86-64, x86 (up to 8 physical CPUs)Windows Server 2008 (R2) w/Hyper-V role, Microsoft Hyper-V ServerSupported drivers for Windows 2000, Windows 2003, Windows 2008, Windows XP, Windows Vista, FreeBSD, Linux (SUSE 10 released, more announced)Proprietary
Hyper-V (2012)Microsoftx86-64 with Intel VT-x or AMD-Vx86-64, (up to 64 physical CPUs)Windows 8, 8.1, 10, and Windows Server 2012 (R2) w/Hyper-V role, Microsoft Hyper-V ServerSupported drivers for Windows NT, FreeBSD, Linux (SUSE 10, RHEL 6, CentOS 6)Proprietary. Component of various Windows editions.
iCore Virtual AccountsiCore Softwarex86x86Windows XPWindows XPProprietary
INTEGRITYGreen Hills SoftwareARM, x86, PowerPCSame as hostLinux, WindowsINTEGRITY native, Linux, Android, AUTOSAR, Windows (on some platforms)Proprietary
Integrity Virtual MachinesHewlett-PackardIA-64IA-64HP-UXHP-UX, Windows, Linux (OpenVMS announced)Proprietary
JPC (Virtual Machine)Oxford UniversityAny running the Java Virtual Machinex86Java Virtual MachineDOS, Linux, Windows up to 3.0GPL version 2
KVMQumranet, now Red Hatx86, x86-64, IA-64, with x86 virtualization, s390, PowerPC,[4]ARM[5]Same as hostLinux, FreeBSD, illumosFreeBSD, Linux, Solaris, Windows, Plan 9GPL version 2
Linux-VServerCommunity projectx86, x86-64, IA-64, Alpha, PowerPC 64, PA-RISC 64, SPARC64, ARM, S/390, SH/66, MIPSCompatibleLinuxLinux variantsGPL version 2
LynxSecureLynuxWorksx86x86No host OSLynxOS, Linux, WindowsProprietary
LXCCommunity project, Canonical Ltd.x86, x86-64, IA-64, PowerPC 64, SPARC64, Itanium, ARMSame as hostLinuxLinux variantsGPL version 2
Mac-on-LinuxMac-on-LinuxPowerPCPowerPCLinuxMac OS X, Mac OS 7.5.2 to 9.2.2, LinuxGPL
Mac-on-MacSebastian GregorzykPowerPCPowerPCMac OS X, up to 10.3Mac OS X, Mac OS 7.5.2 to 9.2.2, LinuxGPL
OKL4 MicrovisorOpen Kernel Labs, acquired by General Dynamics CorporationARM, x86, MIPSARM (v5, v6, v7; paravirtualization), ARMv7VE (hardware virtualization)No Host OSVarious OSes and RTOSes including Linux, Android, QNXProprietary
OpenVZCommunity project, supported by SWsoft, now Parallels, Inc.x86, x86-64, IA-64, PowerPC 64, SPARC64Same as hostLinuxLinux variantsGPL
Oracle VM Server for x86Oracle Corporationx86, x86-64x86, x86-64No host OSMicrosoft Windows, Oracle Linux, Red Hat Enterprise Linux, SolarisGPLv2, Oracle VM Server; Manager is proprietary
OVPsimOVPx86OR1K, MIPS32, ARC600/700, ARM; and public API which enables users to write custom processor models, RISC, CISC, DSP, VLIW all possibleMicrosoft Windows, LinuxDepends on target machine, for example includes MIPS Malta that runs Linux or SMP-Linux; and includes public API which enables users to write custom peripheral and system modelsProprietary, Apache 2.0 for models
Parallels Desktop for MacParallels, Inc.x86x86, x86-64macOSDOS, Windows, Linux, macOS, FreeBSD, OS/2, eComStation, Solaris, HaikuProprietary
Parallels Workstation (discontinued 2013)Parallels, Inc.x86x86Windows, LinuxWindows, Linux, FreeBSD, OS/2, eComStation, DOS, Solaris, HaikuProprietary
PearPCSebastian Biallasx86, x86-64, PowerPCPowerPCWindows, Linux, OS X, FreeBSD, NetBSDMac OS X, Darwin, LinuxGPL
PikeOSSYSGO AGPowerPC, x86, ARM, MIPS, SPARC, SuperHSame as hostNo host OS, Linux or Windows as dev. hostsPikeOS native, Linux, POSIX, AUTOSAR, Android, RTEMS, OSEK, ARINC 653 APEX, ITRONProprietary
Proxmox VEProxmoxx86-64x86, x86-64Debian BasedWindows, Linux, Linux variants, Solaris, FreeBSD, OSx86 (as FreeBSD), virtual appliances, Netware, OS/2, SCO, BeOS, Haiku, DarwinAGPLv3
Oracle VM Server for SPARC (LDoms)Oracle CorporationUltraSPARC T1, UltraSPARC T2, UltraSPARC T2+, SPARC T3, SPARC T4CompatibleSolaris 10, Solaris 11Oracle support: Solaris; unsupported: Linux, FreeBSDProprietary
PowerVMIBMPOWER4, POWER5, POWER6, POWER7, POWER8POWER4/5/6/7/8, x86 (PowerVM-Lx86)PowerVM FirmwareLinux PowerPC, x86; AIX, IBM iProprietary
QEMUFabrice Bellard, other developersx86, x86-64, IA-64, PowerPC, SPARC 32/64, ARM, S/390, MIPSx86, x86-64, Alpha, ARM, CRIS, LM32, M68k, MicroBlaze, MIPS, OpenRisc32, PowerPC, S/390, SH4, SPARC 32/64, Unicore32, XtensaWindows, Linux, macOS, Solaris, FreeBSD, OpenBSD, BeOSChanges regularly[6]GPL/LGPL
QEMU w/ kqemu moduleFabrice Bellardx86, x86-64Same as hostLinux, FreeBSD, OpenBSD, Solaris, WindowsChanges regularly[6]GPL/LGPL
QEMU w/ qvm86 modulePaul Brookx86x86Linux, NetBSD, WindowsChanges regularlyGPL
QuickTransitTransitive Corp.x86, x86-64, IA-64, POWERMIPS, PowerPC, SPARC, x86Linux, OS X, SolarisLinux, OS X, Irix, SolarisProprietary
RTS HypervisorReal-Time Systems GmbHx86, x86-64x86, x86-64No host OSWindows, Linux, Windows Embedded, QNX, RTOS-32, VxWorks, OS-9, T-KernelProprietary
ScaleMP vSMP FoundationScaleMPx86, x86-64Same as hostNo host OSLinuxProprietary
SIMHBob Supnik, The Computer History Simulation ProjectAlpha, ARM, HPPA, x86, IA-64, x86-64, M68K, MIPS, MIPSel, POWER, s390, SPARCData GeneralNova, Eclipse; Digital Equipment CorporationPDP-1, PDP-4, PDP-7, PDP-8, PDP-9, PDP-10, PDP-11, PDP-15, VAX; GRI Corporation GRI-909; IBM1401, 1620, 1130, 7090/7094, System/3; Interdata (Perkin-Elmer) 16b/32b systems; Hewlett-Packard 2114, 2115, 2116, 2100, 21MX; Honeywell H316/H516; MITSAltair 8800 with 8080 and Z80; Royal McBeeLGP-30, LGP-21; Scientific Data SystemsSDS 940BSD, Linux, Solaris, VMS, WindowsDepends on target machine, includes NetBSD/VAX, OpenBSD/VAX, VAX/VMS, Unix v6, Unix v7, TOPS-10, TOPS-20, ITSBSD-like, unique
SimicsWind Riverx86, x86-648051, 68000, ARM (v4, v5, v6, v7), MIPS32, MIPS64, Cavium cnMIPS, Broadcom XLR MIPS, Freescale Power Architecture 32-bit and 64-bit (e300, e500, e600, e5500, e6500), IBM Power Architecture (POWER, PPC44x, PPC46x, 47x), SPARC v8 (LEON), SPARC v9 (UltraSparc), x86 (from 80286 to Sandy Bridge), x86-64 (from Pentium4 to Sandy Bridge), TI TMS320C64xx, Renesas H8, Renesas SHWindows 32-bit and 64-bit, Linux 32-bit and 64-bitDepends on target machine, typically runs unmodified software stacks from the corresponding real target, including VxWorks, VxWorks 653, OSE, QNX, Linux, Solaris, Windows, FreeBSD, RTEMS, TinyOS, Wind River Hypervisor, VMware ESX, and othersProprietary
Sun xVM ServerSun Microsystemsx86-64, SPARCSame as hostNo host OSWindows XP, 2003 Server (x86-64 only), Linux, SolarisGPL version 3
SVISTA 2004Serenity Systems Internationalx86x86Windows, OS/2, LinuxWindows, Linux, OS/2, BSDProprietary
TRANGOTRANGO Virtual Processors, Grenoble, FranceARM, XScale, MIPS, PowerPCParavirtualized ARM, MIPS, PowerPCNo host OS, Linux or Windows as dev. hostsLinux, eCos, µC/OS-II, WindowsCE, Nucleus, VxWorksProprietary
User Mode LinuxJeff Dike, other developersx86, x86-64, PowerPCSame as hostLinuxLinuxGPL version 2
VirtualBoxInnotek, acquired by Oracle Corporationx86, x86-64x86, x86-64 (with Intel VT-x or AMD-V, and VirtualBox 2 or later)Windows, Linux, macOS, Solaris, FreeBSD, eComStationDOS, Linux, macOS,[7] FreeBSD, Haiku, OS/2, Solaris, Syllable, Windows, and OpenBSD (with Intel VT-x or AMD-V, due to otherwise tolerated incompatibilities in the emulated memory management).[8]GPL version 2; full version with extra enterprise features is proprietary:
Virtual Iron 3.1Virtual Iron Software, Inc., acquired by Oraclex86 VT-x, x86-64 AMD-Vx86, x86-64No host OSWindows, LinuxProprietary, some components GPLv2[9]
Virtual PC 2007 (discontinued)Connectix and Microsoftx86, x86-64x86Windows Vista (Business, Enterprise, Ultimate), XP Pro, XP Tablet PC EditionDOS, Windows, OS/2, Linux (SUSE, Xubuntu), OpenSolaris (Belenix)Proprietary
Windows Virtual PC (discontinued)Connectix and Microsoftx86, x86-64 with Intel VT-x or AMD-Vx86Windows 7Windows XP, Windows Vista, Windows 7, Windows Server 2003, Windows Server 2008Proprietary
Virtual PC 7 for MacConnectix and MicrosoftPowerPCx86Mac OS XWindows, OS/2, LinuxProprietary
VirtualLogix VLXVirtualLogixARM, TI DSP C6000, x86, PowerPCSame as hostNo host OSLinux, Windows XP, C5, VxWorks, Nucleus, DSP/BIOS, proprietaryProprietary
Virtual Server 2005 R2Connectix and Microsoftx86, x86-64x86, x86-64Windows Server 2003, 2008, XP (Requires IIS)Windows NT, 2000, 2003, 2008, Linux (Red Hat, SUSE, Ubuntu)Proprietary
Synopsys (CoWare)Virtual PlatformCoWarex86, x86-64, SPARC v9Devices including (multi) cores from ARM, MIPS, PowerPC, ToshibaMeP, Renesas SH, Texas Instruments, Tensilica, ZSPWindows, Linux, SolarisDepends on guest CPU; includes: Linux (various flavors), µITRON (various flavors), Windows CE, Symbian, moreProprietary
VirtuozzoSWsoft, now Virtuozzo Incx86, IA-64, x86-64x86, IA-64, x86-64Linux, WindowsLinux, WindowsProprietary
VMmanagerISPsystemx64x64LinuxLinuxProprietary
VMware ESX ServerVMwarex86, x86-64x86, x86-64No host OSWindows, Linux, Solaris, FreeBSD, OSx86 (as FreeBSD), virtual appliances, Netware, OS/2, SCO, BeOS, Haiku, Darwin, others: runs arbitrary OS[a]Proprietary
VMware ESXiVMwarex86, x86-64x86, x86-64No host OSSame as VMware ESX ServerProprietary
VMware FusionVMwarex86, x86-64x86, x86-64macOSSame as VMware ESX ServerProprietary
VMware ServerVMwarex86, x86-64x86, x86-64Windows, LinuxSame as VMware ESX ServerProprietary
VMware WorkstationVMwarex86-64[b]x86, x86-64Windows, LinuxSame as VMware ESX ServerProprietary
VMware Player, later VMware Workstation PlayerVMwarex86-64[c]x86, x86-64Windows, LinuxSame as VMware ESX ServerProprietary, free for personal non-commercial use[10][11]
Wind River HypervisorWind Riverx86, x86-64, PowerPC, ARMSame as hostNo host OSLinux, VxWorks, unmodified guests (including MS Windows and RTOSes such ach OSE, QNX and others), bare metal virtual boardProprietary
XenXensource, Now Citrix Systemsx86, x86-64, ARM, IA-64 (inactive), PowerPC (inactive)Same as hostGNU/Linux, Unix-likeGNU/Linux, FreeBSD, MiniOS, NetBSD, Solaris, Windows 7/XP/Vista/Server 2008 (requires Intel VT-x (Vanderpool) or AMD-V (Pacifica)-capable CPU), Plan 9GNU GPLv2 +
XenServerBy Citrix Systemsx86, x86-64, ARM, IA-64 (inactive), PowerPC (inactive)Same as hostNo host OSGNU/Linux, FreeBSD, MiniOS, NetBSD, Solaris, Windows 7/XP/Vista/Server 2008 (with Intel VT-x or AMD-V), Plan 9GNU GPLv2 +
XtratuMUniversidad Politecnica de Valenciax86, x86; SPARC v8 LEON2/3Same as hostNo host OSGPOS: Linux, RTOS: PartiKle, RTEMSGPL
z/VMIBMz/Architecturez/Architecture, z/VM does not run on predecessor mainframesNo host OS, itself (single or multiple levels/versions deep; e.g., VM/ESA running in z/VM 4.4 in z/VM 5.2 in z/VM 5.1.)Linux on zSeries, z/OS, z/VSE, z/TPF, z/VM, VM/CMS, MUSIC/SP, OpenSolaris for System z, predecessorsProprietary
z LPARsIBMz/Architecturez/ArchitectureIntegrated in firmware of System z mainframesLinux on zSeries, z/OS, z/VSE, z/TPF, z/VM, MUSIC/SP, and predecessorsProprietary
NameCreatorHost CPUGuest CPUHost OS(s)Guest OS(s)License

Features[edit]

NameGuest OS SMP availableRuns arbitrary OSSupported guest OS driversMethod of operationTypical useSpeed relative to host OSCommercial support available
Containers, or ZonesYes, over 500-way on current systemsNoUses native device driversOperating system-level virtualizationServer consolidation with workload isolation, single workload containment, hosting, dev/test/prodNear nativeYes
Hyper-V Server 2008 R2Yes, up to 4 VCPUs per VMYesYesVirtualizationServer consolidation, service continuity, dev/test, desktop virtualization, cloud computingUp to near native[citation needed][3]Yes
OpenVZYesNoCompatibleOperating system-level virtualizationVirtualized server isolationUp to near native[citation needed][4]Yes
KVMYes[12]YesYesAMD-V and Intel-VT-xVirtualized server isolation, server/desktop consolidation, software development, cloud computing, other purposesUp to near native[citation needed][5]Yes[13]
Linux-VServerYesNoCompatibleOperating system-level virtualizationVirtualized server isolation and security, server consolidation, cloud computingUp to near native[citation needed][6]Yes
Oracle VM Server for x86YesYesYesParavirtualization and hardware virtualizationServer consolidation and security, enterprise and business deploymentUp to near native[citation needed]Yes
Oracle VM Server for SPARC (LDoms)YesYes, but needs porting[14]YesParavirtualization and hardware virtualizationServer consolidation and security, enterprise and business deploymentUp to near native[citation needed]Yes
OVPsimYesYes?Full system simulation with optional component virtualizationSoftware development (early, embedded), advanced debug for single and multicore software, compiler and other tool development, computer architecture research, hobbyistDepends on target architecture (full and slow hardware emulation for guests incompatible with host)[citation needed]Yes, with commercial license from Imperas[15]
PikeOSYesYes, but modifications required as paravirtualization is usedYesParavirtualizationSafety and security critical embedded systems.Up to near native[citation needed]Yes
ScaleMP vSMP FoundationYes, up to 8,192 CPUs and 64 TB per VM[citation needed]YesYesVirtualizationServer consolidation, Cloud computing ?Yes
SimicsYesYesYesFull system simulation of processors, MMUs, devices, disks, memories, networks, etc.Software development, advanced debug for single and multicore software, compiler and other tool development, computer architecture research, bug transportation, automated testing, system architecture, long-term support of safety-critical systems, early hardware availability, virtual prototypingDepends on host machine and target architecture. Runs at near-native speeds for x86-on-x86 using VT-x, cross-simulation of other architectures can be faster or slower than real-time depending on how fast the target is and how big the target is (number of processors, number of target machines, and how much the simulation can be parallelized)Yes
Sun xVM ServerYesYesYesParavirtualization and porting or hardware virtualizationServers, DevelopmentUp to near native[citation needed]Yes
SVISTA 2004No???Hobbyist, Developer, Business workstation??
TRANGOYesYes[7]YesParavirtualization and porting or hardware virtualizationMob. phone, STB, routers, etc.Near native[8][citation needed]?
User Mode Linux?Nospecial guest kernel+modules requiredPortingDeveloper (as a separate machine for a server or with X11 networking)Non-significantly slower than native [9] (all calls to kernel are proxied)[citation needed]?
OKL4 MicrovisorYesYes, (either with para-virtualization or HW virtualization)YesParavirtualization, Hardware assisted virtualizationMobile, embedded, security, safety critical, networking, legacy OS, etc.Near nativeYes
Oracle VirtualBoxYesYesYesVirtualizationBusiness workstation, server consolidation, service continuity, developer, hobbyistUp to near native[citation needed]Yes (with commercial license)
Virtual Iron 3.1Yes, up to 8 wayYesYesNative virtualizationServer consolidation, service continuity, dev/test ?Yes
Virtual PC 2007NoYesYesVirtualization, guest calls trapping where supportedHobbyist, Developer, Business workstationUp to near native[citation needed] with virtual machine additions?
Windows Virtual PCYesYesYesHardware virtualizationDeveloper, Business workstation, support for Compatibility with Windows XP applicationsUp to near native[citation needed] with virtual machine additionsNo
Virtual PC 7 for MacNoYesYesdynamic recompilation (guest calls trapping where supported)Hobbyist, Developer, Business workstationSlow[citation needed]?
Virtual Server 2005 R2NoYesYesVirtualization (guest calls trapping where supported)Server, server farmUp to near native with virtual machine additions but slower than with hypervisor due to proxied calls[citation needed]?
CoWareVirtual PlatformYesYesYes ( Same compiled Software image as for the real device)Full-system virtualization (Processor Core ISA + Hardware + External connections)Early embedded software development and integration (from driver to application), Multi-core software debugging and optimizationDepending on the system characteristics and the software itself, ranges from faster than real time to slow[citation needed].Yes
VirtuozzoYesNoCompatibleOperating system-level virtualizationServer consolidation, service continuity, disaster recovery, service providersUp to near native[citation needed]Yes
VMware ESXi Server 5.5 (vSphere)Yes, add-on, up to 64 wayNoYesVirtualizationServer consolidation, service continuity, dev/test, cloud computing, business critical applications, Infrastructure as a Service IaaSUp to near native[citation needed]Yes
VMware ESX Server 4.0 (vSphere)Yes, add-on, up to 8 wayYesYesVirtualizationServer consolidation, service continuity, dev/test, cloud computingUp to near native[citation needed]Yes
VMware ESX Server 3.0Yes, add-on, up to 4 wayYesYesVirtualizationServer consolidation, service continuity, dev/testUp to near native[citation needed]Yes
VMware ESX Server 2.5.3Yes, add-on, 2 wayYesYesVirtualizationServer consolidation, service continuity, dev/testUp to near native[citation needed]Yes
VMware FusionYesYesYesVirtualizationHobbyist, Developer, Tester, Business workstationUp to near native[citation needed]Yes
VMware ServerYes (2-way)YesYesVirtualizationServer/desktop consolidation, dev/testUp to near native[citation needed]Yes
VMware WorkstationYes (2-way)YesYesParavirtualization (VMI) and virtualizationTechnical professional, advanced dev/test, trainerUp to near native[citation needed]Yes
VMware PlayerYes[16]YesYesVirtualizationTechnical professional, advanced dev/test, trainer, end user on prebuilt machinesUp to near native[citation needed]No
XenYes, v4.0.0: up to 128 VCPUs per VMNoYesParavirtualization and porting or hardware virtualizationVirtualized server isolation, server/desktop consolidation, software development, cloud computing, other purposes. Xen powers most public cloud services and many hosting services, such as Amazon Web Services, Rackspace Hosting and Linode.Up to native[17]Yes
XenServerYesYesYesParavirtualization and porting or hardware virtualizationVirtualized server isolation, server/desktop consolidation, software development, cloud computing, other purposes. Xen powers most public cloud services and many hosting services, such as Amazon Web Services, Rackspace Hosting and Linode.Up to native[17]Yes
XtratuMYesNoYesParavirtualizationEmbedded, safety critical, secure?Yes
z/VMYes, both real and virtual (guest perceives more CPUs than installed), incl. dynamic CPU provisioning and reassignmentYesYes, but not requiredVirtualization (among first systems to provide hardware assists)ServersNear native[10]Yes
z LPARsYes, both real and virtual (guest perceives more CPUs than installed), incl. dynamic CPU provisioning and reassignment; up to 64 real coresYesYes, but not requiredMicrocode and hardware hypervisorServersNative: System z machines always run with at least one LPARYes
NameGuest OS SMP availableRuns arbitrary OSSupported guest OS driversMethod of operationTypical useSpeed relative to host OSCommercial support available
  • ^ Providing any virtual environment usually requires some overhead of some type or another. Native usually means that the virtualization technique does not do any CPU level virtualization (like Bochs), which executes code more slowly than when it is directly executed by a CPU. Some other products such as VMWare and Virtual PC use similar approaches to Bochs and QEMU, however they use a number of advanced techniques to shortcut most of the calls directly to the CPU (similar to the process that JIT compiler uses) to bring the speed to near native in most cases. However, some products such as coLinux, Xen, z/VM (in real mode) do not suffer the cost of CPU-level slowdowns as the CPU-level instructions are not proxied or executing against an emulated architecture since the guest OS or hardware is providing the environment for the applications to run under. However access to many of the other resources on the system, such as devices and memory may be proxied or emulated in order to broker those shared services out to all the guests, which may cause some slow downs as compared to running outside of virtualization.
  • ^ OS-level virtualization is described as "native" speed, however some groups have found overhead as high as 3% for some operations, but generally figures come under 1%, so long as secondary effects do not appear.
  • ^ See[18] for a paper comparing performance of paravirtualization approaches (e.g. Xen) with OS-level virtualization
  • ^ Requires patches/recompiling.
  • ^ Exceptional for lightweight, paravirtualized, single-user VM/CMS interactive shell: largest customers run several thousand users on even single prior models. For multiprogramming OSes like Linux on zSeries and z/OS that make heavy use of native supervisor state instructions, performance will vary depending on nature of workload but is near native. Hundreds into the low thousands of Linux guests are possible on a single machine for certain workloads.

Image type compatibility[edit]