A system virtual machine (also called SysVM) is a
virtual machine
In computing, a virtual machine (VM) is the virtualization or emulator, emulation of a computer system. Virtual machines are based on computer architectures and provide the functionality of a physical computer. Their implementations may involve ...
(VM) that provides a complete
system platform
A computing platform, digital platform, or software platform is the infrastructure on which software is executed. While the individual components of a computing platform may be obfuscated under layers of abstraction, the ''summation of the requi ...
and supports the
execution
Capital punishment, also known as the death penalty and formerly called judicial homicide, is the state-sanctioned killing of a person as punishment for actual or supposed misconduct. The sentence ordering that an offender be punished in ...
of a complete
operating system
An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ...
(OS). These usually
emulate an existing
architecture
Architecture is the art and technique of designing and building, as distinguished from the skills associated with construction. It is both the process and the product of sketching, conceiving, planning, designing, and construction, constructi ...
, and are built with the purpose of either providing a
platform to run programs where the real
hardware is not available for use (for example, executing on otherwise obsolete platforms), or of having multiple instances of virtual machines leading to more efficient use of computing resources, both in terms of energy consumption and cost effectiveness (known as
hardware 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 emulates the hardw ...
, the key to a
cloud computing
Cloud computing is "a paradigm for enabling network access to a scalable and elastic pool of shareable physical or virtual resources with self-service provisioning and administration on-demand," according to International Organization for ...
environment), or both. A VM was originally defined by
Popek and Goldberg as "an efficient, isolated duplicate of a real machine".
System virtual machines
System virtual machine advantages:
* Multiple OS environments can co-exist on the same primary hard drive, with a virtual partition that allows sharing of files generated in either the "host" operating system or "guest" virtual environment. Adjunct software installations, wireless connectivity, and remote replication, such as printing and faxing, can be generated in any of the guest or host operating systems. Regardless of the system, all files are stored on the hard drive of the host OS.
* Application provisioning, maintenance, high availability and disaster recovery are inherent in the virtual machine software selected.
* Can provide
emulated hardware environments different from the host's
instruction set architecture
In computer science, an instruction set architecture (ISA) is an abstract model that generally defines how software controls the CPU in a computer or a family of computers. A device or program that executes instructions described by that ISA, ...
(ISA), through emulation or by using
just-in-time compilation
In computing, just-in-time (JIT) compilation (also dynamic translation or run-time compilations) is compilation (of computer code) during execution of a program (at run time) rather than before execution. This may consist of source code transl ...
.
The main disadvantages of VMs are:
* A virtual machine is less efficient than an actual machine when it accesses the host hard drive indirectly.
* When multiple VMs are concurrently running on the hard drive of the actual host, adjunct virtual machines may exhibit a varying and/or unstable performance (speed of execution and malware protection). This depends on the data load imposed on the system by other VMs, unless the selected VM software provides
temporal isolation among virtual machines.
* Malware protections for VMs are not necessarily compatible with the "host", and may require separate software.
Multiple VMs running their own guest operating system are frequently engaged for server consolidation in order to avoid interference from separate VMs on the same actual machine platform.
The desire to run multiple operating systems was the initial motivation for virtual machines, so as to allow time-sharing among several single-tasking operating systems. In some respects, a system virtual machine can be considered a generalization of the concept of
virtual memory
In computing, virtual memory, or virtual storage, is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a ver ...
that historically preceded it. IBM's
CP/CMS, the first systems to allow
full virtualization, implemented
time sharing
In computing, time-sharing is the concurrent sharing of a computing resource among many tasks or users by giving each task or user a small slice of processing time. This quick switch between tasks or users gives the illusion of simultaneous ...
by providing each user with a single-user operating system, the
CMS. Unlike virtual memory, a system virtual machine entitled the user to write privileged instructions in their code. This approach had certain advantages, such as adding input/output devices not allowed by the standard system.
As technology evolves virtual memory for purposes of virtualization, new systems of
memory overcommitment Memory overcommitment is a concept in computing that covers the assignment of more memory to virtual computing devices (or processes) than the physical machine they are hosted, or running on, actually has. This is possible because virtual machines ( ...
may be applied to manage memory sharing among multiple virtual machines on one actual computer operating system. It may be possible to share "memory pages" that have identical contents among multiple virtual machines that run on the same physical machine, what may result in mapping them to the same physical page by a technique known as
Kernel SamePage Merging
In computing, kernel same-page merging (KSM), also known as kernel shared memory, memory merging, memory deduplication, and page deduplication is a kernel feature that makes it possible for a hypervisor system to share memory pages that have id ...
. This is particularly useful for read-only pages, such as those that contain code segments; in particular, that would be the case for multiple virtual machines running the same or similar software, software libraries, web servers, middleware components, etc. The guest operating systems do not need to be compliant with the host hardware, thereby making it possible to run different operating systems on the same computer (e.g.,
Microsoft Windows
Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...
,
Linux
Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...
, or previous versions of an operating system) to support future software.
The use of virtual machines to support separate guest operating systems is popular in regard to
embedded systems
An embedded system is a specialized computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is em ...
. A typical use would be to run a
real-time operating system
A real-time operating system (RTOS) is an operating system (OS) for real-time computing applications that processes data and events that have critically defined time constraints. A RTOS is distinct from a time-sharing operating system, such as Unix ...
simultaneously with a preferred complex operating system, such as Linux or Windows. Another use would be for novel and unproven software still in the developmental stage, so it runs inside a
sandbox
A sandbox is a sandpit, a wide, shallow playground construction to hold sand, often made of wood or plastic.
Sandbox or sand box may also refer to:
Arts, entertainment, and media
* Sandbox (band), a Canadian rock music group
* Sandbox (Gu ...
. Virtual machines have other advantages for operating system development, and may include improved debugging access and faster reboots.
Techniques
Different virtualization techniques are used, based on the desired usage. ''Native execution'' is based on direct virtualization of the underlying raw hardware, thus it provides multiple "instances" of the same
architecture
Architecture is the art and technique of designing and building, as distinguished from the skills associated with construction. It is both the process and the product of sketching, conceiving, planning, designing, and construction, constructi ...
a real machine is based on, capable of running complete operating systems. Some virtual machines can also
emulate different architectures and allow execution of software applications and operating systems written for another
CPU
A central processing unit (CPU), also called a central processor, main processor, or just processor, is the primary processor in a given computer. Its electronic circuitry executes instructions of a computer program, such as arithmetic, log ...
or architecture.
Operating-system-level virtualization
OS-level virtualization is an operating system (OS) virtualization paradigm in which the kernel allows the existence of multiple isolated user space instances, including containers ( LXC, Solaris Containers, AIX WPARs, HP-UX SRP Containers, ...
allows the resources of a computer to be partitioned via
kernel
Kernel may refer to:
Computing
* Kernel (operating system), the central component of most operating systems
* Kernel (image processing), a matrix used for image convolution
* Compute kernel, in GPGPU programming
* Kernel method, in machine learnin ...
's support for multiple isolated
user space
A modern computer operating system usually uses virtual memory to provide separate address spaces or regions of a single address space, called user space and kernel space. This separation primarily provides memory protection and hardware prote ...
instances, which are usually called
containers
A container is any receptacle or enclosure for holding a product used in storage, packaging, and transportation, including shipping.
Things kept inside of a container are protected on several sides by being inside of its structure. The term ...
and may look and feel like real machines to the
end user
In product development, an end user (sometimes end-user) is a person who ultimately uses or is intended to ultimately use a product. The end user stands in contrast to users who support or maintain the product, such as sysops, system administrato ...
s. Some computer architectures are capable of
hardware-assisted virtualization
In computing, virtualization (abbreviated v12n) is a series of technologies that allows dividing of physical computing resources into a series of virtual machines, operating systems, processes or containers.
Virtualization began in the 1960s with ...
, which enables efficient full virtualization by using virtualization-specific hardware capabilities, primarily from the host CPUs.
Virtualization of the underlying raw hardware (native execution)
This approach is described as
full virtualization of the hardware, and can be implemented using a type 1 or type 2
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 called ...
: a type 1 hypervisor runs directly on the hardware, and a type 2 hypervisor runs on another operating system, such as
Linux
Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...
or
Windows
Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...
. Each virtual machine can run any operating system supported by the underlying hardware. Users can thus run two or more different "guest" operating systems simultaneously, in separate "private" virtual computers.
The pioneer system using this concept was IBM's
CP-40, the first (1967) version of IBM's
CP/CMS (1967–1972) and the precursor to IBM's
VM family (1972–present). With the VM architecture, most users run a relatively simple
interactive computing
In computer science, interactive computing refers to software which accepts input from the user as it runs.
Interactive software includes commonly used programs, such as word processors or spreadsheet applications. By comparison, non-interactiv ...
single-user operating system,
CMS, as a "guest" on top of the VM control program (
VM-CP). This approach kept the CMS design simple, as if it were running alone; the control program quietly provides multitasking and resource management services "behind the scenes". In addition to CMS communication and other system tasks are performed by multitasking VMs (RSCS, GCS, TCP/IP, UNIX), and users can run any of the other IBM operating systems, such as
MVS
Multiple Virtual Storage, more commonly called MVS, is the most commonly used operating system on the System/370, System/390 and IBM Z IBM mainframe computers. IBM developed MVS, along with OS/VS1 and SVS, as a successor to OS/360. It is unr ...
, even a new CP itself or now
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:
...
. Even the simple CMS could be run in a threaded environment (LISTSERV, TRICKLE).
z/VM
z/VM is the current version in IBM's VM family of virtual machine operating systems. First released in October 2000, z/VM remains in active use and development . It is directly based on technology and concepts dating back to the 1960s, particu ...
is the current version of VM, and is used to support hundreds or thousands of virtual machines on a given mainframe. Some installations use
Linux on IBM Z
Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...
to run
Web server
A web server is computer software and underlying Computer hardware, hardware that accepts requests via Hypertext Transfer Protocol, HTTP (the network protocol created to distribute web content) or its secure variant HTTPS. A user agent, co ...
s, where
Linux
Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...
runs as the operating system within many virtual machines.
Full virtualization is particularly helpful in operating system development, when experimental new code can be run at the same time as older, more stable, versions, each in a separate virtual machine. The process can even be
recursive
Recursion occurs when the definition of a concept or process depends on a simpler or previous version of itself. Recursion is used in a variety of disciplines ranging from linguistics to logic. The most common application of recursion is in m ...
:
IBM
International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...
debugged new versions of its virtual machine operating system,
VM, in a virtual machine running under an older version of VM, and even used this technique to simulate new hardware.
[See History of CP/CMS for IBM's use of virtual machines for operating system development and simulation of new hardware]
The standard
x86
x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel, based on the 8086 microprocessor and its 8-bit-external-bus variant, the 8088. Th ...
instruction set architecture
In computer science, an instruction set architecture (ISA) is an abstract model that generally defines how software controls the CPU in a computer or a family of computers. A device or program that executes instructions described by that ISA, ...
as used in the modern PCs does not actually meet the
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 " ...
. Notably, there is no execution mode where all sensitive machine instructions always trap, which would allow per-instruction virtualization.
Despite these limitations, several software packages have managed to provide
virtualization on the x86 architecture, even though
dynamic recompilation
In computer science, dynamic recompilation is a feature of some emulators and virtual machines, where the system may recompile some part of a program during execution. By compiling during execution, the system can tailor the generated code to ...
of privileged code, as first implemented by
VMware, incurs some performance overhead as compared to a VM running on a natively virtualizable architecture such as the IBM System/370 or
Motorola MC68020. By now, several other software packages such as
Virtual PC
Virtual PC is a discontinued x86 emulator software for Microsoft Windows hosts and PowerPC-based Mac (computer), Mac hosts. It was created by Connectix in 1997 and acquired by Microsoft in 2003, after which the program was renamed Microsoft V ...
,
VirtualBox
Oracle VirtualBox (formerly Sun VirtualBox, Sun xVM VirtualBox and InnoTek VirtualBox) is a hosted hypervisor for x86 virtualization developed by Oracle Corporation. VirtualBox was originally created by InnoTek Systemberatung GmbH, which was ac ...
,
Parallels Workstation and
Virtual Iron manage to implement virtualization on x86 hardware.
Intel
Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California, and Delaware General Corporation Law, incorporated in Delaware. Intel designs, manufactures, and sells computer compo ...
and
AMD
Advanced Micro Devices, Inc. (AMD) is an American multinational corporation and technology company headquartered in Santa Clara, California and maintains significant operations in Austin, Texas. AMD is a hardware and fabless company that de ...
have introduced
features to their x86 processors to enable
virtualization in hardware.
As well as virtualization of the resources of a single machine, multiple independent nodes in a cluster can be combined and accessed as a single virtual
NUMA
Numa or NUMA may refer to:
* Non-uniform memory access (NUMA), in computing
Places
* Numa Falls, a waterfall in Kootenay National Park, Canada
* 15854 Numa, a main-belt asteroid
United States
* Numa, Indiana
* Numa, Iowa
* Numa, Oklahoma
* ...
machine.
Emulation of a non-native system
Virtual machines can also perform the role of an
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 sof ...
, allowing software applications and
operating systems
An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ...
written for another
computer processor
Cryptominer, In computing and computer science, a processor or processing unit is an electrical component (circuit (computer science), digital circuit) that performs operations on an external data source, usually Memory (computing), memory or som ...
architecture to be run.
Operating-system-level virtualization
Operating-system-level virtualization is a server
virtualization
In computing, virtualization (abbreviated v12n) is a series of technologies that allows dividing of physical computing resources into a series of virtual machines, operating systems, processes or containers.
Virtualization began in the 1960s wit ...
technology which virtualizes
server
Server may refer to:
Computing
*Server (computing), a computer program or a device that provides requested information for other programs or devices, called clients.
Role
* Waiting staff, those who work at a restaurant or a bar attending custome ...
s on an
operating system
An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ...
(kernel) layer. It can be thought of as partitioning: a single physical server is sliced into multiple small partitions (otherwise called virtual environments (VE),
virtual private server
A virtual private server (VPS) or virtual dedicated server (VDS) is a virtual machine sold as a service by an Internet hosting company.
A virtual private server runs its own copy of an operating system (OS), and customers may have superuser- ...
s (VPS), guests, zones, etc.); each such partition looks and feels like a real server, from the point of view of its users.
For example, Solaris Zones supports multiple guest operating systems running under the same operating system such as Solaris 10. Guest operating systems can use the same kernel level with the same operating system version, or can be a separate copy of the operating system with a different kernel version using Solaris Kernel Zones.
Solaris native Zones also requires that the host operating system is a version of Solaris; other operating systems from other manufacturers are not supported. However, Solaris Branded Zones would need to be used to have other operating systems as zones.
Another example is
System Workload Partitions (WPARs), introduced in version 6.1 of the IBM AIX operating system. System WPARs are software partitions running under one instance of the global AIX OS environment.
The operating system level architecture has low overhead that helps to maximize efficient use of server resources. The virtualization introduces only a negligible overhead and allows running hundreds of
virtual private server
A virtual private server (VPS) or virtual dedicated server (VDS) is a virtual machine sold as a service by an Internet hosting company.
A virtual private server runs its own copy of an operating system (OS), and customers may have superuser- ...
s on a single physical server. In contrast, approaches such as
full virtualization (like
VMware) and
paravirtualization
In computing, virtualization (abbreviated v12n) is a series of technologies that allows dividing of physical computing resources into a series of virtual machines, operating systems, processes or containers.
Virtualization began in the 1960s with ...
(like
Xen or
UML) cannot achieve such level of density, due to overhead of running multiple kernels. From the other side, operating system-level virtualization does not allow running different operating systems (i.e., different kernels), although different libraries, distributions, etc. are possible. Different virtualization techniques are used, based on the desired usage. Native execution is based on direct virtualization of the underlying raw hardware, thus it provides multiple "instances" of the same architecture a real machine is based on, capable of running complete operating systems. Some virtual machines can also emulate different architectures and allow execution of software applications and operating systems written for another CPU or architecture. Operating-system-level virtualization allows the resources of a computer to be partitioned via kernel's support for multiple isolated user space instances, which are usually called containers and may look and feel like real machines to the end users. Some computer architectures are capable of hardware-assisted virtualization, which enables efficient full virtualization by using virtualization-specific hardware capabilities, primarily from the host CPUs.
Virtualization-enabled hardware
Examples of virtualization-enabled hardware include the following:
*
Alcatel-Lucent
Alcatel-Lucent S.A. () was a multinational telecommunications equipment company, headquartered in Boulogne-Billancourt, Paris, France. The company focused on Fixed line telephone, fixed, Mobile phone, mobile and telecommunications convergence, ...
3B20D/3B21D emulated on
commercial off-the-shelf
Commercial-off-the-shelf or commercially available off-the-shelf (COTS) products are packaged or canned (ready-made) hardware or software, which are adapted aftermarket to the needs of the purchasing organization, rather than the commissioning of ...
computers with 3B2OE or 3B21E system
*
ARM TrustZone
ARM (stylised in lowercase as arm, formerly an acronym for Advanced RISC Machines and originally Acorn RISC Machine) is a family of RISC instruction set architectures (ISAs) for computer processors. Arm Holdings develops the ISAs and licen ...
* Boston Circuits gCore (grid-on-chip) with 16
ARC 750D cores and Time-machine hardware virtualization module.
*
Freescale
Freescale Semiconductor, Inc. was an American semiconductor manufacturer. It was created by the divestiture of the Semiconductor Products Sector of Motorola in 2004. Freescale focused their integrated circuit products on the automotive, embedde ...
PowerPC
PowerPC (with the backronym Performance Optimization With Enhanced RISC – Performance Computing, sometimes abbreviated as PPC) is a reduced instruction set computer (RISC) instruction set architecture (ISA) created by the 1991 Apple Inc., App ...
MPC8572 and MPC8641D
*
IBM
International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...
System/360 Model 67,
System/370
The IBM System/370 (S/370) is a range of IBM mainframe computers announced as the successors to the IBM System/360, System/360 family on June 30, 1970. The series mostly maintains backward compatibility with the S/360, allowing an easy migrati ...
,
System/390
The IBM System/390 is a discontinued mainframe product family implementing ESA/390, the fifth generation of the System/360 instruction set architecture. The first computers to use the ESA/390 were the Enterprise System/9000 (ES/9000) fa ...
, and
zSeries
IBM Z is a family name used by IBM for all of its z/Architecture mainframe computers.
In July 2017, with another generation of products, the official family was changed to IBM Z from IBM z Systems; the IBM Z family will soon include the newes ...
mainframes
*
IBM Power Systems
IBM Power Systems is a family of server computers from IBM that are based on its Power processors. It was created in 2008 as a merger of the System p and System i product lines.
History
IBM had two distinct POWER- and PowerPC-based hardwa ...
*
x86
x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel, based on the 8086 microprocessor and its 8-bit-external-bus variant, the 8088. Th ...
:
**
AMD-V
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- ...
(formerly code-named Pacifica)
**
Intel VT-x
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-a ...
(formerly code-named Vanderpool)
*
HP vPAR and cell based
nPAR
*
GE and
Honeywell
Honeywell International Inc. is an American publicly traded, multinational conglomerate corporation headquartered in Charlotte, North Carolina. It primarily operates in four areas of business: aerospace, building automation, industrial automa ...
Multics systems
*
Honeywell
Honeywell International Inc. is an American publicly traded, multinational conglomerate corporation headquartered in Charlotte, North Carolina. It primarily operates in four areas of business: aerospace, building automation, industrial automa ...
200/2000 systems Liberator replacing IBM 14xx systems
*
Honeywell
Honeywell International Inc. is an American publicly traded, multinational conglomerate corporation headquartered in Charlotte, North Carolina. It primarily operates in four areas of business: aerospace, building automation, industrial automa ...
Level 62/64/66
*
IBM System/360
The IBM System/360 (S/360) is a family of mainframe computer systems announced by IBM on April 7, 1964, and delivered between 1965 and 1978. System/360 was the first family of computers designed to cover both commercial and scientific applicati ...
and
System/370
The IBM System/370 (S/370) is a range of IBM mainframe computers announced as the successors to the IBM System/360, System/360 family on June 30, 1970. The series mostly maintains backward compatibility with the S/360, allowing an easy migrati ...
models with emulators supporting programs for older IBM systems
*
Honeywell Level 6 minicomputers emulated predecessor 316/516/716 minis
*
Oracle Corporation
Oracle Corporation is an American Multinational corporation, multinational computer technology company headquartered in Austin, Texas. Co-founded in 1977 in Santa Clara, California, by Larry Ellison, who remains executive chairman, Oracle was ...
(previously
Sun Microsystems
Sun Microsystems, Inc., often known as Sun for short, was an American technology company that existed from 1982 to 2010 which developed and sold computers, computer components, software, and information technology services. Sun contributed sig ...
) SPARC sun4v (
SPARC M6,
T5,
T4,
T3,
UltraSPARC T1
The UltraSPARC T1 (codenamed "Niagara") is a Multithreading (computer architecture), multithreading, Multi-core processor, multicore central processing unit, CPU released by Sun Microsystems in 2005. Designed to lower the energy consumption of s ...
and
T2) utilized by
Oracle VM Server for SPARC, also known as "Logical Domains"
*
Xerox Sigma 6 CPUs were modified to emulate GE/Honeywell 600/6000 systems
See also
*
Amazon Machine Image
*
Linux containers
*
Storage hypervisor
Software-defined storage (SDS) is a marketing term for computer data storage software for policy-based provisioning and management of data storage independent of the underlying hardware. Software-defined storage typically includes a form of storag ...
*
Universal Turing machine
In computer science, a universal Turing machine (UTM) is a Turing machine capable of computing any computable sequence, as described by Alan Turing in his seminal paper "On Computable Numbers, with an Application to the Entscheidungsproblem". Co ...
*
Virtual appliance
A virtual appliance is a pre-configured virtual machine image, ready to run on a hypervisor; virtual appliances are a subset of the broader class of software appliances. Installation of a software appliance on a virtual machine and packaging that ...
*
Virtual backup appliance
VMware Infrastructure is a collection of virtualization products from VMware. Virtualization is an abstraction layer that decouples hardware from operating systems. The VMware Infrastructure suite allows enterprises to optimize and manage their ...
*
Virtual disk image
In computer science, storage virtualization is "the process of presenting a logical view of the physical storage resources to" a host computer system, "treating all storage media (hard disk, optical disk, tape, etc.) in the enterprise as a sing ...
*
Virtual machine escape
Notes
References
Further reading
* James E. Smith, Ravi Nair, ''Virtual Machines: Versatile Platforms For Systems And Processes'', Morgan Kaufmann, May 2005, , 656 pages (covers both process and system virtual machines)
* Craig, Iain D. ''Virtual Machines''.
Springer
Springer or springers may refer to:
Publishers
* Springer Science+Business Media, aka Springer International Publishing, a worldwide publishing group founded in 1842 in Germany formerly known as Springer-Verlag.
** Springer Nature, a multinationa ...
, 2006, , 269 pages (covers only process virtual machines)
External links
The Reincarnation of Virtual Machines, Article on ACM Queue by Mendel Rosenblum, Co-Founder, VMware
{{DEFAULTSORT:Virtual Machine
*
Operating system technology