Virtual Machine

A Virtual Machine (VM) presents virtualised hardware — vCPUs, memory, storage, and network interfaces — to a guest operating system. The guest OS runs unmodified, believing it controls dedicated physical hardware. The hypervisor (VMM) running on the physical host multiplexes actual hardware resources across multiple VMs, enforcing isolation between them.

In datacentre contexts, VMs are the fundamental unit of Infrastructure-as-a-Service (IaaS) offerings from cloud providers (AWS EC2, Azure Virtual Machines, Google Compute Engine) and on-premise virtualisation platforms (VMware vSphere, Microsoft Hyper-V, KVM/QEMU). VM density on modern servers ranges from tens to hundreds per physical host depending on workload type. VMs provide stronger isolation than containers but carry higher overhead; bare metal servers are used where maximum performance or regulatory isolation is required.