A Virtual Machine (VM) is a software-based emulation of a physical computer. It operates as an independent and isolated instance of an operating system (OS) running on a host machine. Virtualization technology allows multiple virtual machines to coexist on a single physical server, each running its own OS and applications.
Key characteristics of virtual machines include:
- Each virtual machine is isolated from other VMs running on the same host. This isolation ensures that the operations or failures in one VM do not affect others.
- Virtual machines are independent entities with their own virtualized hardware resources, including virtual CPU, memory, storage, and network interfaces. This independence allows them to run different operating systems and applications simultaneously on the same physical hardware.
- VMs are portable and can be moved between different physical hosts with compatible hypervisors. This portability is advantageous for tasks like load balancing, disaster recovery, and resource optimization.
- Resource Allocation:
- Virtual machines share the physical resources of the host machine, such as CPU, memory, and storage. The hypervisor, or Virtual Machine Monitor (VMM), manages the allocation of these resources to each VM based on their configurations and resource demands.
- Flexibility and Scalability:
- Virtualization allows for the creation and deletion of virtual machines as needed. This flexibility enables quick provisioning of new VMs and the ability to scale resources up or down based on demand.
- Snapshot and Cloning:
- Virtual machines can be easily cloned or snapshot at a specific point in time. Cloning creates an identical copy of a VM, while snapshots capture the VM’s state for backup or recovery purposes.
- Live Migration:
- Many virtualization platforms support live migration, allowing VMs to be moved from one physical host to another without causing downtime. This feature is useful for load balancing, maintenance, and improving resource utilization.
- Testing and Development:
- Virtualization is widely used in testing and development environments. VMs provide a sandboxed and replicable environment for software development, testing, and debugging.
Common virtualization platforms for creating and managing virtual machines include VMware, Microsoft Hyper-V, KVM (Kernel-based Virtual Machine), and Oracle VM VirtualBox.
In summary, virtual machines enable the efficient use of physical hardware by allowing multiple operating systems and applications to run on a single host machine. They play a crucial role in server consolidation, resource optimization, and the overall flexibility of IT infrastructure.