A hypervisor is software that enables a computer to run multiple operating systems through virtualization, presenting a virtual set of hardware to all software. It manages the flow of information between software, virtualized hardware, and physical hardware. Hypervisors use virtualization to create simulated sets of hardware, known as virtual machines. They intercept restricted functions before they reach the hardware and execute them in a way that doesn’t harm other operating systems. Hypervisors can be found in consumer and enterprise products and help consolidate underutilized servers running different operating systems.
A hypervisor is a unique type of software that allows a computer to run more than one operating system (OS). Through a process known as virtualization, software tricks each operating system into thinking it has exclusive access to a particular set of hardware. It sits between the physical hardware and the operating system and presents a virtual set of hardware to all other software running on the machine. It also manages the flow of information between the software, virtualized hardware and physical hardware. This type of software is used in both consumer and corporate settings.
In most cases, a computer’s operating system runs in a highly privileged state where it has unrestricted access to the machine’s hardware while applications run in a less privileged state and have to rely on the operating system. These different levels of hardware access privileges are known as rings, with the operating system traditionally running in ring 0; user applications run in rings 1–3, which have fewer privileges. This model works fine most of the time, but completely falls apart when trying to run more than one operating system on a single computer at the same time. A hypervisor solves this problem using a technique called virtualization.
Virtualization is not a new idea, but it has become a buzzword since the mid-2000s as businesses and the information technology (IT) industry realized its potential to reduce costs and increase productivity. efficiency. There are many different approaches to virtualization, but the basic idea is to create simulated sets of hardware, often known as virtual machines. In the case of a hypervisor, which can also be called a virtual machine monitor, each virtual machine contains a “guest” operating system. The hypervisor itself can either run directly on physical hardware, in which case it is known as a “bare metal” type, or within a host operating system as a “software” hypervisor.
Hypervisors have to use some very sophisticated techniques to manage their guest operating systems and make sure they don’t conflict with each other. Because an operating system inside a virtual machine is unaware that it has been stripped of ring 0 privileges, it may attempt to perform restricted functions without permission. In these cases, the hypervisor can intercept a function before it reaches the hardware, execute the instructions in a way that doesn’t harm other operating systems running on the hardware, and return the result to the original operating system. Known as a “trap and emulate” technique, this is just one of many advanced concepts unique to the world of virtualization.
As this type of software has become more important and profitable, more and more companies have looked for ways to lighten the load on a hypervisor and provide better performance. Software vendors have modified their operating systems to be aware of the virtual machines they are running on, which means fewer types of trapping and emulation scenarios. Hardware vendors have added support for a new privilege level sometimes known as ring -1. Newer software programs can take advantage of one or both of these techniques to increase performance.
Hypervisors can now be found in a variety of products at both consumer and enterprise levels. Consumer products that allow one operating system to run inside another often use a software-type hypervisor. In the corporate space, the software helps consolidate underutilized servers running different operating systems. Software developers might use this approach to run multiple instances of similar or even identical operating systems to check for compatibility issues.
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