Virtualization or virtualization technology is originated in IBM in the late 1960.It allows concurrent execution of multiple operating system with thereapplications on the same physical machine.

In physical machine there is c.p.u.,memory,disk and devices, if these resoruces is shared by multiple applications with there corresponding operating system on there machines which are vitrual machines,so concurrent execution execution of multiple operating system with there app licationson a same hardware simultaneously is possible by virtualization.









So virtualization allow concurrent execution of multiple operating system on same physical machine.

Virtual machine

So in this single hardware there are such virtual machines resides, so a virtual machine consists of operating system,its applications and virtual resoruces.

At each virtual machine its operating system thinnks that it owns all the hardware resoruces of the physical machine and other operating system of other virtual machine thinks that it owns all the physical resoruces, this is called virtual resoruces.The operating ssytem of all virtual machine s is called guest OS.Physical kardwareare shared among these vierual machines that why it is called vierual resources.









Guest OS is accessing or own entire hardware or some part of it ,guest OS view hardware like these.

Hypervisor (virtual machine monitor)

To create virtualization of creating virtual machines from physucal machine hardware, it requires a layer which is called virtualization layer or you cn also called operating system of all different ooperating systems also called hypervisor or virtual machine monitor.

Virtualization layer or hypervisor or virtual machine mpmonitor supports operating system of different virtial machines or actially maanges the physical resources to be allocated to these different operating system amd its applications runing on it.

Hypervisor provides or manages the physical hardware resoruces and also provide virtualized view to the several operating system which are guest OS.

Virtual machine is an efficient isolation of duplicate of the original real machine which is supported by virtual machine monitor.

Hypervisor or virtual machine monitor will provide the environment that is essentially identical to the original machine so the all physucal hardware resiruces are avaiable as a part of the physical machine will means that these guest operating system have an illusion that they owning the physical hardware resrouces and this illusion is supported by virtual machine monitor or hypervisor.

This illusion is achieved in real sense or in real as it is copy of all physical resources will be available as a part of vierual resources to the guest operating system.Hence the main goal of hypervisor is feedility.

The secomd goal of the hypervisor is that program show the minor decrease in the speed.As all hardware resoruces are shared between different operating system as , all hardware resrouces is not avaailable to particular guest OS, it is shared so there is minor decrease in performance of program, virtual machine takes care of it.

The third goal of virtual machine monitor is that it is in full control of physical hardware resoruces so if it is in not infull control one guest OS interfere with other guest OS, It achieves isolation and safety between several guest OS.

Hypervisor has full controlled on the physical hardware resoruces which allows to give controlled access ti the hardware resources to multiple virtual machines with there operating system.

Benefits of virtualization

Here are some benefots pf vortia;ozatopn

Consolidation

Consolidation is the ability to runmultiple virtual machine with there operating system and its applications on single physical platform, it will decrease overall cost as physical hardware resrouces is not fully utliized by single set of physical operating system and its applications,so runing several muluiple virtual machines on same physical hardware oobviously decrease cost and also improves maangeability of these resources and also decreases electricity bills and other maintenance costs.

Migration

Migratuin here means migrating virtual machines from one physical machine to other physical machine, virtual machines are detached and these virtual machines are migrated or copied to other olaces when there is scope of improvement,availability and improving reliability, there are some reasons to migrat eentire virtual machine from one physical macine to another physical machine thereby increasing availability,inproving reliability and also increase system performance.So here maintenance is quite automatic and manageable.

Security

In virtualization operating system and applications are nicely encapsulated in virtual machines, these virtual machines work and operate indepemdemtly and separately so it is easy to detect any error,malicious behaviour and bugs so any kind of problem occur in a particular virtual machine will not effect the working of other virtual machines.

Types of hypervisor

Bare metal hypervisor

Bare metal hypervisor is also called native hypervisor and also known as type 1 hypervisor.This hypervisor is sitting just above the physical hardware allow runing diffrtrnt typrd of OO’s which is not possible earlier.

Bare metal hy=upervisor sits above the physical hardware and maanges all physical hardware resoruces and it also supports multiple virtual machines with the help of privileaged service virtual machine.

Privileage service virtual machine deals with devices,configuration and other maangement tasks.For example devices to be shared between several machine is done by privileage service virtual machine.

Example of bare metal hypervisor are ZEn virtualization and VMware.

Hosted hypervisor

Hosted hypervisor is also known as type 2 hypervisor.In ths hypervisor physical hardware has a operating system whcih is called host operating system or hosted operatig system.To run multiple different operating system, hypervisor is hosted on this host operating system so this hypervisor is called hosted hypervisor.In this model first is physical hardware then host operating system sits on then, then hypervisor sits on the host operating system.

In hosted hypervisor physical hardware is at lowest and host operating system resides just above physical hardware and manages hardware resoruces.Ths hosted operating system integrates the virtual machine monitor which is called hosted hypervisor, this hosted hypervisor suppoers and maanges several virtual machines woth its guest OS and its application.

Host operating system manages devices which is shared to several virtual machines via hosted hypervisor.

In hosted hypervisor physical hardware is managed by host operating system ,hosted hypervisor resides on hosted operating system and it shares all physical hardware to several virtual machines bycommunication and managing with host operating system

Example of hosted hypervisor is KVM.