Many of today's cutting-edge technologies, such as cloud computing,edge computingymicrosserviços,They owe their origin to the virtual machine concept, which separates operating systems and software instances from the underlying physical computer.
What is a virtual machine?
A virtual machine (VM) is software that runs programs or applications without being tied to a physical machine. In a VM instance, one or more guest machines can run on a host computer.
Each VM has its own operating system and runs separately from other VMs, even if they are located on the same physical host. Virtual machines usually run on servers, but they can also run on desktop systems or even embedded platforms. Multiple virtual machines can share a physical host's resources, including CPU cycles, network bandwidth, and memory.
Virtual machines track yourorigins to early daysof computing in the 1960s, when timesharing for mainframe users was used to separate software from a physical host system. A virtual machine was defined in the early 1970s as "an efficient, isolated duplicate of a real computer".
VMs, as we know them today, have gained traction over the past 20 years as enterprises have embracedserver virtualizationto use the computing power of its physical servers more efficiently, reducing the number of physical servers and saving space in the data center. Because applications with different operating system requirements could run on a single physical host, different server hardware was not required for each one.
How do virtual machines work?
In general, there are two types of virtual machines: process virtual machines, which separate a single process, and system virtual machines, which provide complete separation of the operating system and applications from the physical computer. Examples of computing virtual machines include the Java virtual machine, the .NET Framework, and the Parrot virtual machine.
The system's virtual machines are based onhypervisorsas an intermediary that provides software access to hardware resources. The hypervisor emulates the computer's CPU, memory, hard disk, network, and other hardware resources, creating a pool of resources that can be assigned to individual virtual machines according to their specific requirements. The hypervisor can support multiple virtual hardware platforms that are isolated from each other, allowing virtual machines to run Linux and Windows Server operating systems on the same physical host.
Big names in the hypervisor space include VMware (ESX/ESXi), Intel/Linux Foundation (Xen), Oracle (MV Server for SPARC and Oracle VM Server for x86), and Microsoft (Hyper-V).
Desktop computer systems can also use virtual machines. An example here would be a Mac user running a virtual instance of Windows on their physical Mac hardware.
What are the two types of hypervisors?
The hypervisor manages resources and assigns them to virtual machines. It also schedules and adjusts how resources are distributed based on how the hypervisor and virtual machines have been configured, and can reallocate resources as demand fluctuates. Most hypervisors fall into one of two categories:
- Type 1.The Abare-metal hypervisor runs directly on the physical host machine and has direct access to its hardware. Type 1 hypervisors generally run on servers and are considered to be more efficient and perform better than Type 2 hypervisors, making them suitable for server, desktop and application virtualization. Examples of Type 1 hypervisors include Microsoft Hyper-V and VMware ESXi.
- Type 2.Sometimes called a hosted hypervisor, a type 2 hypervisor is installed on top of the host machine's operating system, which manages calls to hardware resources. Type 2 hypervisors are typically deployed on end-user systems for specific use cases. For example, a developer might use a type 2 hypervisor to create a specific environment to build an application, or a data analyst might use it to test an application in an isolated environment. Examples include VMware Workstation and Oracle VirtualBox.
What are the advantages of virtual machines?
Because the software is separate from the physical host computer, users can run multiple instances of the operating system on a single piece of hardware, saving the company time, administrative costs, and physical space. Another advantage is that virtual machines can support legacy applications, reducing or eliminating the need and cost of migrating an old application to a different or updated operating system.
Additionally, developers use virtual machines to test applications in a secure, isolated environment. Developers who want to see if their applications will work on a new operating system can use virtual machines to test their software instead of buying new hardware and operating system upfront. For example, Microsoft recently updated its free Windows virtual machines that allow developers todownload a trial VM with Windows 11to test the operating system without upgrading a main computer.
This can also help isolate malware that might infect a given VM instance. Since software inside a VM cannot tamper with the host computer, malicious software cannot spread as much damage.
What are the disadvantages of virtual machines?
Virtual machines have some disadvantages. Running multiple virtual machines on a physical host can lead to unstable performance, especially if the infrastructure requirements of a given application are not met. This also makes them less efficient in many cases compared to a physical computer.
And if the physical server fails, all running applications will stop working. Most IT shops use a balance between physical and virtual systems.
What are some other forms of virtualization?
The success of virtual machines in server virtualization has led to virtualization being applied to other areas such as storage, networking and desktops. Most likely, if there is a type of hardware used in thedata center, the concept of virtualization is being explored (for example,application delivery controllers).
In network virtualization, companies exploitednetwork as a serviceoptions andnetwork role virtualization(NFV), which uses basic servers to replace specialized network devices to enable more flexible and scalable services. This differs somewhat from software-defined networking, which separates the network control plane from the forwarding plane to allow for more automated provisioning and policy-based management of network resources. A third technology,virtual network functions, are software-based services that can run in an NFV environment, including processes such as routing, firewalling, load balancing, WAN acceleration, and encryption.
Verizon, for example, uses NFV to power itsvirtual network servicesthat allows customers to activate new services and features on demand. Services include virtual appliances, routing, software-defined WANs, WAN optimization, and even Session Border Controller as a Service (SBCaaS) to centrally manage and securely deploy IP-based real-time services such as VoIP and unified communications.
Virtual machines and containers
The growth of virtual machines has led to the development of technologies such as containers, which take the concept a step further and are gaining popularity among web application developers. In a containerized configuration, a single application can be virtualized along with its dependencies. With much less overhead than a virtual machine, a container just contains binaries, libraries and applications.
While some think that container development cankill the virtual machine, there are enough features and benefits of virtual machines to keep the technology moving forward. For example, virtual machines are still useful when running multiple applications together or running legacy applications on older operating systems.
Furthermore, some feel that the containers areless secure than VM hypervisorsbecause containers have only one operating system which is shared by applications whereas virtual machines can isolate application and operating system.
Gary Chen, research manager for Software Defined Computing at IDC, said the VM software market remains a core technology even as customers explore cloud architectures and containers. “The virtual machine software market has been remarkably resilient and will continue to grow positively over the next five years despite being very mature and approaching saturation,” writes Chen at IDC.Global Virtual Machine Software Forecast, 2019-2022.
Virtual Machines, 5G, and Edge Computing
Virtual machines are considered part of new technologies such as 5G and edge computing. For example, Virtual Desktop Infrastructure (VDI) providers like Microsoft, VMware and Citrix are looking at ways to extend their VDI systems to employees now working from home as part of a post-COVID hybrid model.
“With VDI, you need extremely low latency because you're essentially sending keystrokes and mouse movements to a remote desktop,” says Mahadev Satyanarayanan, professor of computer science at Carnegie Mellon University. In 2009, Satyanarayanan wrote about how virtual machine-based cloudlets could be used to bring better processing capabilities to mobile devices at the Internet edge, leading to the development of edge computing.
In the 5G wireless space, the process ofnetwork cutuses software-defined networking and NFV technologies to help install networking functionality into virtual machines on a virtualized server to provide services that previously only ran on proprietary hardware.
Like many other technologies in use today, these emerging innovations would not have been developed had it not been for the original VM concepts introduced decades ago.
Keith Shaw is a freelance digital journalist who has been writing about the IT world for over 20 years.
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Keith Shaw is a digital journalist and content creator with over 20 years covering technology. He is currently the host of Foundry's "Today in Tech" show.
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