Platform virtualization software, specifically
emulator
In computing, an emulator is Computer hardware, hardware or software that enables one computer system (called the ''host'') to behave like another computer system (called the ''guest''). An emulator typically enables the host system to run so ...
s and
hypervisor
A hypervisor (also known as a virtual machine monitor, VMM, or virtualizer) is a type of computer software, firmware or hardware that creates and runs virtual machines. A computer on which a hypervisor runs one or more virtual machines is calle ...
s, are
software packages that emulate the whole physical computer machine, often providing multiple
virtual machine
In computing, a virtual machine (VM) is the virtualization/emulation of a computer system. Virtual machines are based on computer architectures and provide functionality of a physical computer. Their implementations may involve specialized hardw ...
s on one physical platform. The table below compares basic information about
platform virtualization
Hardware virtualization is the virtualization of computers as complete hardware platforms, certain logical abstractions of their componentry, or only the functionality required to run various operating systems. Virtualization hides the physica ...
hypervisors.
General
Features
* 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
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 IBM Z
Linux on IBM Z or Linux on zSystems is the collective term for the Linux operating system compiled to run on IBM mainframes, especially IBM Z / IBM zSystems and IBM LinuxONE servers. Similar terms which imply the same meaning are ''Linux/390'', ...
and
z/OS
z/OS is a 64-bit operating system for IBM z/Architecture mainframes, introduced by IBM in October 2000. It derives from and is the successor to OS/390, which in turn was preceded by a string of MVS versions.Starting with the earliest:
* O ...
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
Other features
* Windows Server 2008 R2 SP1 and Windows 7 SP1 have limited support for redirecting the USB protocol over
RDP using
RemoteFX Microsoft RemoteFX is a Microsoft brand name that covers a set of technologies that enhance visual experience of the Microsoft-developed remote display protocol Remote Desktop Protocol (RDP). RemoteFX was first introduced in Windows Server 2008 R2 ...
.
* Windows Server 2008 R2 SP1 adds accelerated graphics support for certain editions of Windows Server 2008 R2 SP1 and Windows 7 SP1 using RemoteFX.
Restrictions
This table is meant to outline restrictions in the software dictated by licensing or capabilities.
Note: No limit means no enforced limit. For example, a VM with 1 TB of memory cannot fit in a host with only 8 GB memory and no memory swap disk, so it will have a limit of 8 GB physically.
See also
*
List of computer system emulators
This article lists software and hardware that emulates computing platforms.
The host in this article is the system running the emulator, and the guest is the system being emulated.
The list is organized by '' guest operating system'' (the syste ...
*
Comparison of application virtualization software
*
Comparison of OS emulation or virtualization apps on Android
There are many apps in Android that can run or emulate other operating systems, via utilizing hardware support for platform virtualization technologies, or via terminal emulation. Some of these apps support having more than one emulation/virtual ...
*
Popek and Goldberg virtualization requirements
The Popek and Goldberg virtualization requirements are a set of conditions sufficient for a computer architecture to support system virtualization efficiently. They were introduced by Gerald J. Popek and Robert P. Goldberg in their 1974 article "F ...
*
Virtual DOS machine
Virtual DOS machines (VDM) refer to a technology that allows running 16-bit/32-bit DOS and 16-bit Windows programs when there is already another operating system running and controlling the hardware.
Overview
Virtual DOS machines can operate ei ...
*
x86 virtualization
x86 virtualization is the use of hardware-assisted virtualization capabilities on an x86/x86-64 CPU.
In the late 1990s x86 virtualization was achieved by complex software techniques, necessary to compensate for the processor's lack of hardware-as ...
Notes
References
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[Look a]
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for details
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Platform virtualization software
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 i ...