In computing, virtualization or virtualisation ( sometimes abbreviated v12n, a numeronym ) is the act of creating a virtual ( quite than actual ) version of something, including virtual calculator hardware platforms, storehouse devices, and calculator network resources. Virtualization began in the 1960s, as a method of logically dividing the system resources provided by central processing unit computers between different applications. Since then, the mean of the term has broadened. [ 1 ]
Hardware virtualization [edit ]
Hardware virtualization or platform virtualization refers to the creation of a virtual machine that acts like a real computer with an manoeuver system. Software executed on these virtual machines is separated from the underlying hardware resources. For model, a calculator that is running Microsoft Windows may host a virtual machine that looks like a calculator with the Ubuntu Linux operating arrangement ; Ubuntu-based software can be run on the virtual machine. [ 2 ] [ 3 ]
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In hardware virtualization, the host machine is the machine that is used by the virtualization and the guest machine is the virtual machine. The words host and guest are used to distinguish the software that runs on the physical machine from the software that runs on the virtual machine. The software or firmware that creates a virtual machine on the host hardware is called a hypervisor or virtual machine monitor. Different types of hardware virtualization include :
- Full virtualization – almost complete simulation of the actual hardware to allow software environments, including a guest operating system and its apps, to run unmodified.
- Paravirtualization – the guest apps are executed in their own isolated domains, as if they are running on a separate system, but a hardware environment is not simulated. Guest programs need to be specifically modified to run in this environment.
Hardware-assisted virtualization is a room of improving overall efficiency of virtualization. It involves CPUs that provide corroborate for virtualization in hardware, and other hardware components that help improve the performance of a node environment. Hardware virtualization can be viewed as part of an overall tendency in enterprise IT that includes autonomic calculate, a scenario in which the IT environment will be able to manage itself based on perceive action, and utility computer science, in which calculator processing baron is seen as a utility that clients can pay for merely as needed. The usual goal of virtualization is to centralize administrative tasks while improving scalability and overall hardware-resource utilization. With virtualization, several operating systems can be run in parallel on a individual central march whole ( CPU ). This parallelism tends to reduce overhead costs and differs from multitasking, which involves running respective programs on the like OS. Using virtualization, an enterprise can better manage updates and rapid changes to the operating system and applications without disrupting the user. “ ultimately, virtualization dramatically improves the efficiency and handiness of resources and applications in an constitution. rather of relying on the old model of “ one waiter, one application ” that leads to underutilized resources, virtual resources are dynamically applied to meet business needs without any excess fat ” ( ConsonusTech ). Hardware virtualization is not the like as hardware emulation. In hardware emulation, a assemble of hardware imitates another, while in hardware virtualization, a hypervisor ( a nibble of software ) imitates a finical nibble of computer hardware or the entire calculator. Furthermore, a hypervisor is not the lapp as an copycat ; both are calculator programs that imitate hardware, but their world of practice in speech differs .
Snapshots [edit ]
A snapshot is a state of a virtual machine, and generally its storage devices, at an demand point in meter. A snapshot enables the virtual machine ‘s state at the time of the snapshot to be restored late, efficaciously undoing any changes that occurred afterwards. This capability is useful as a stand-in technique, for model, anterior to performing a bad operation. virtual machines frequently use virtual disks for their storehouse ; in a very childlike case, a 10- gigabyte hard magnetic disk drive is simulated with a 10-gigabyte flat charge. Any requests by the VM for a placement on its physical magnetic disk are transparently translated into an process on the correspond charge. once such a translation layer is award, however, it is potential to intercept the operations and send them to unlike files, depending on diverse criteria. Every fourth dimension a snapshot is taken, a modern file is created, and used as an overlay for its predecessors. New data is written to the topmost overlie ; reading existing data, however, needs the sheathing hierarchy to be scanned, resulting in accessing the most recent version. frankincense, the integral stack of snapshots is about a individual coherent phonograph record ; in that sense, creating snapshots works similarly to the incremental accompaniment proficiency. other components of a virtual machine can besides be included in a snapshot, such as the contents of its random-access memory ( RAM ), BIOS settings, or its shape settings. “ Save state “ feature in video game comfort emulators is an example of such snapshots. Restoring a snapshot consists of discarding or disregarding all overlie layers that are added after that snapshot, and directing all raw changes to a new overlie .
migration [edit ]
The snapshots described above can be moved to another host machine with its own hypervisor ; when the VM is temporarily stopped, snapshotted, moved, and then resumed on the newly host, this is known as migration. If the older snapshots are kept in synchronize regularly, this process can be quite debauched, and allow the VM to provide continuous service while its anterior physical horde is, for model, taken down for physical maintenance .
Failover [edit ]
similar to the migration mechanism described above, failover allows the VM to continue operations if the host fails. Generally it occurs if the migration has stopped working. however, in this casing, the VM continues operation from the last-known coherent state of matter, preferably than the current state, based on whatever materials the backup server was concluding provide with.
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Video game console emulation [edit ]
A video game cabinet copycat is a platform that allows a personal computer or television game comfort to emulate a different video recording game console ‘s behavior. Video game cabinet emulators and hypervisors both perform hardware virtualization ; words like “ virtualization ”, “ virtual machine ”, “ host ” and “ guest ” are not used in concurrence with console table emulators .
Nested virtualization [edit ]
Nested virtualization refers to the ability of running a virtual machine within another, having this general concept extendible to an arbitrary astuteness. In other words, nested virtualization refers to running one or more hypervisors inside another hypervisor. nature of a nest guest virtual machine does not need not be homogeneous with its host virtual machine ; for exemplar, application virtualization can be deployed within a virtual machine created by using hardware virtualization. [ 4 ] Nested virtualization becomes more necessity as widespread operating systems gain built-in hypervisor functionality, which in a virtualized environment can be used only if the surrounding hypervisor supports nested virtualization ; for example, Windows 7 is capable of running Windows XP applications inside a built-in virtual car. Furthermore, moving already existing virtualized environments into a swarm, following the Infrastructure as a Service ( IaaS ) set about, is much more complicate if the destination IaaS platform does not support nest virtualization. [ 5 ] [ 6 ] The way cuddle virtualization can be implemented on a finical calculator computer architecture depends on support hardware-assisted virtualization capabilities. If a particular architecture does not provide hardware accompaniment required for nest virtualization, versatile software techniques are employed to enable it. [ 5 ] Over time, more architectures gain required hardware defend ; for example, since the Haswell microarchitecture ( announced in 2013 ), Intel started to include VMCS shadowing as a technology that accelerates nest virtualization. [ 7 ]
Licensing [edit ]
virtual machines running proprietary operational systems require license, regardless of the host machine ‘s function organization. For exercise, installing Microsoft Windows into a VM node requires its license requirements to be satisfied. [ 8 ] [ 9 ] [ 10 ]
Desktop virtualization [edit ]
Desktop virtualization is the concept of separating the logical desktop from the physical machine. One shape of desktop virtualization, virtual background infrastructure ( VDI ), can be thought of as a more promote form of hardware virtualization. Rather than interacting with a host computer directly via a keyboard, mouse, and admonisher, the drug user interacts with the host computer using another desktop computer or a fluid device by means of a network joining, such as a LAN, Wireless LAN or tied the Internet. In addition, the host calculator in this scenario becomes a waiter calculator capable of hosting multiple virtual machines at the same time for multiple users. [ 11 ] As organizations continue to virtualize and converge their data kernel environment, client architectures besides continue to evolve in rate to take advantage of the predictability, continuity, and choice of service delivered by their converge infrastructure. For exemplar, companies like HP and IBM provide a hybrid VDI mannequin with a range of virtualization software and delivery models to improve upon the limitations of distribute customer computing. [ 12 ] Selected client environments move workloads from PCs and other devices to data center servers, creating well-managed virtual clients, with applications and client operate environments hosted on servers and storehouse in the data center. For users, this means they can access their desktop from any location, without being tied to a one customer device. Since the resources are centralized, users moving between ferment locations can hush access the same node environment with their applications and data. [ 12 ] For IT administrators, this means a more centralize, effective customer environment that is easier to maintain and able to more cursorily respond to the changing needs of the user and commercial enterprise. [ 13 ] Another shape, session virtualization, allows multiple users to connect and log into a shared but powerful calculator over the network and use it simultaneously. Each is given a background and a personal folder in which they store their files. [ 11 ] With multiseat configuration, session virtualization can be accomplished using a individual personal computer with multiple monitors, keyboards, and shiner connected. thin clients, which are seen in desktop virtualization, are simple and/or cheap computers that are chiefly designed to connect to the network. They may lack significant hard phonograph record storage quad, RAM or even processing power, but many organizations are beginning to look at the monetary value benefits of eliminating “ thick node ” desktops that are packed with software ( and require software licensing fees ) and making more strategic investments. [ 14 ] Desktop virtualization simplifies software versioning and patch management, where the new double is just updated on the server, and the background gets the update version when it reboots. It besides enables centralized restraint over what applications the user is allowed to have access to on the workstation. Moving virtualized desktops into the cloud creates hosted virtual desktops ( HVDs ), in which the desktop images are centrally managed and maintained by a specialist hosting tauten. Benefits include scalability and the reduction of capital consumption, which is replaced by a monthly operational price. [ 15 ]
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Containerization [edit ]
Operating-system-level virtualization, besides known as containerization, refers to an operate system feature of speech in which the kernel allows the universe of multiple sequester user-space instances. such instances, called containers, [ 16 ] partitions, virtual environments ( VEs ) or jails ( FreeBSD imprison or chroot imprison ), may look like real computers from the point of view of programs running in them. A computer program running on an ordinary operate system can see all resources ( connected devices, files and folders, network shares, CPU power, quantifiable hardware capabilities ) of that computer. however, programs running inside a container can only see the container ‘s contents and devices assigned to the container. Containerization started gaining bulge in 2014, with the introduction of Docker. [ 17 ] [ 18 ]
other types [edit ]
- Memory virtualization: aggregating random-access memory (RAM) resources from networked systems into a single memory pool
- Virtual memory: giving an app the impression that it has contiguous working memory, isolating it from the underlying physical memory implementation
- Data virtualization: the presentation of data as an abstract layer, independent of underlying database systems, structures and storage
- Database virtualization: the decoupling of the database layer, which lies between the storage and application layers within the application stack over all
- Network virtualization: creation of a virtualized network addressing space within or across network subnets
- Virtual private network (VPN): a network protocol that replaces the actual wire or other physical media in a network with an abstract layer, allowing a network to be created over the Internet
See besides [edit ]
References [edit ]
- An Introduction to Virtualization, January 2004, by Amit Singh