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Virtualization

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Virtualization abstracts physical hardware so multiple isolated operating systems can share the same host. It is the foundation of modern data centers, cloud platforms, and many industrial server consolidations.

Overview

The hypervisor presents virtual CPUs, memory, storage, and network adapters to each VM. Modern CPUs (Intel VT-x, AMD-V, ARM virt) provide hardware extensions that make this near-native in performance.

Hypervisor Types

  • Type 1 (bare-metal) — ESXi, Hyper-V Server, KVM, Xen, Proxmox VE.
  • Type 2 (hosted) — VMware Workstation/Fusion, VirtualBox, Parallels.

Core Concepts

  • vCPU pinning, NUMA awareness, CPU ready time.
  • Memory overcommit, ballooning, transparent page sharing.
  • Thin vs thick provisioning.
  • Snapshots — point-in-time; not a backup.
  • Live migration (vMotion, Hyper-V Live Migration) — zero-downtime moves.
  • SR-IOV and PCIe pass-through for high-performance I/O.

VMs vs Containers

  • VM — full OS, strong isolation, heavier (GBs).
  • Container — shared kernel, lightweight (MBs), faster start.
  • Both have a place; many environments run containers on top of VMs.

Platforms

  • VMware vSphere / ESXi + vCenter — enterprise standard.
  • Microsoft Hyper-V + System Center / Failover Clustering.
  • KVM / QEMU + libvirt — Linux native.
  • Proxmox VE — KVM + LXC web UI.
  • Nutanix AHV, Citrix XenServer, Oracle VM.
  • HCI: Nutanix, vSAN, Azure Stack HCI.

Operations

  • Right-size VMs — over-allocated vCPUs hurt performance.
  • Use clusters with HA + DRS / affinity rules.
  • Back up at hypervisor level (Veeam, Commvault, Nakivo).
  • Patch hosts in rolling maintenance with live migration.
  • Monitor CPU ready, memory swap, storage latency.
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