Virtual Machine – Definition and meaning
What is Virtual Machine? Find out what a virtual machine is and how it is used in virtualisation technology.
What is a virtual machine?
A virtual machine (VM) is a software emulation of a physical computer that makes it possible to run applications in an isolated environment. VMs simulate the hardware of a real computer, including CPU, RAM, hard disks and network devices, allowing multiple operating systems to be run simultaneously on a single physical computer. This is particularly used in server environments for server virtualisation.
Functions and advantages of virtual machines
Virtual machines offer numerous advantages, including
- Cost efficiency: by consolidating multiple VMs on a single physical server, organisations can significantly reduce hardware costs.
- Flexibility: VMs can be created, copied and deleted quickly, significantly speeding up development and testing.
- Isolation: Applications running in a VM are isolated from the host system and other VMs, resulting in increased security.
- Portability: VMs can be easily migrated to other physical machines, enabling flexible application deployment.
Types of virtual machines
There are two main types of virtual machines:
1. System Virtual Machines
System VMs emulate complete physical hardware and enable the execution of a complete operating system. Examples include hypervisor-based VMs such as VMware and Microsoft Hyper-V.
2. Process Virtual Machines
Process VMs provide a platform for specific applications and usually only run one application. An example of this is the Java Virtual Machine (JVM), which runs Java applications independently of the operating system.
How do virtual machines work?
Virtual machines are based on hypervisors that act as intermediaries between the hardware and the virtual machines. There are two main types of hypervisors:
- Type 1 hypervisor: Runs directly on the hardware (e.g. VMware ESXi, Microsoft Hyper-V).
- Type 2 hypervisor: Runs on an existing operating system (e.g. VMware Workstation, Oracle VirtualBox).
The hypervisor manages the resources and ensures that the VMs are operated securely and in isolation, while at the same time providing them with the required resources.
Use cases for virtual machines
The application of virtual machines is diverse and ranges from:
- Test and development environments: Developers use VMs to test software in isolated environments.
- Cloud computing: Providers such as AWS, Google Cloud and Microsoft Azure rely heavily on VMs to scale resources efficiently.
- Secure environments: VMs can be used for security-critical applications to minimise the impact of malware or security incidents.
Illustrative example on the topic: Virtual Machine
Imagine you are a software developer who wants to test a new application for different operating systems. You have a powerful laptop with Windows 10, but you also need to test Linux and macOS on it. Instead of procuring additional physical machines, you decide to create several virtual machines.
You set up a Linux VM to test the server version of your application and a macOS VM to make sure everything is working properly. Within minutes, you have created your test environments, can test all components in isolation from each other and quickly make changes if necessary. This flexibility and efficiency shows just how powerful and useful virtual machines are.
Conclusion
Virtual machines are an indispensable tool in the modern IT infrastructure. They offer a cost-effective, flexible and secure way of providing and testing software and services. With the increasing importance of cloud computing and virtualisation technologies, VMs will continue to play a central role in the IT world. For more information on related topics, visit our encyclopaedia on cloud computing or containers.
Frequently asked questions
Virtual machines offer numerous advantages, including cost efficiency, flexibility, isolation and portability. By consolidating multiple VMs on one physical server, companies can significantly reduce hardware costs. VMs also enable rapid creation and deletion, which speeds up development and testing processes. The isolation of applications increases security, while the portability of VMs allows easy migration to other physical machines.
System Virtual Machines emulate complete physical hardware and allow the execution of a complete operating system, while Process Virtual Machines provide a platform for specific applications and usually only run one application. An example of a system VM is VMware, while the Java Virtual Machine (JVM) serves as a process VM. This distinction is important for selecting the right virtualisation solution depending on the use case.
In the cloud, virtual machines are based on hypervisors that act as an intermediary between physical hardware and VMs. Cloud providers such as AWS and Microsoft Azure mainly use Type 1 hypervisors that run directly on the hardware. This enables efficient resource utilisation and scalability, as VMs can be created and managed dynamically to meet user requirements.
In software development, virtual machines are often used for test and development environments. Developers can test different operating systems and software configurations in isolation without having to purchase additional physical hardware. This flexibility makes it possible to quickly make adjustments and simulate different scenarios, which significantly increases efficiency in the development process.
Virtual machines offer significant security benefits as they run applications in isolated environments. This isolation protects the host system and other VMs from potential threats such as malware or security incidents. If a VM is compromised, the integrity of the other VMs and the host system is maintained, which is particularly important in security-critical applications.