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3.3.1. Virtualization Concepts (Hypervisors, VMs, Containers)

šŸ’” First Principle: A hypervisor is the core software that creates and manages virtual machines, enabling multiple, isolated operating systems to run concurrently on a single physical host.

Scenario: You need to set up a server that will host several production virtual machines for different departments. For maximum performance and stability, you choose a Type 1 (bare-metal) hypervisor like VMware ESXi, which runs directly on the server hardware.

Virtualization allows you to get more value out of your physical hardware.

  • Hypervisor: The software that enables virtualization.
    • Type 1 (Bare-metal): Runs directly on the host's hardware. Offers the best performance. Examples: VMware ESXi, Microsoft Hyper-V. Used in data centers.
    • Type 2 (Hosted): Runs as an application on top of an existing OS (like Windows or macOS). Easier to set up and use. Examples: VMware Workstation, Oracle VirtualBox. Used for desktop virtualization.
  • Virtual Machine (VM): A complete, isolated guest operating system running on a hypervisor. Each VM has its own virtualized hardware (CPU, RAM, storage, network).
    • Use Cases: Server consolidation, testing and development, running legacy applications.
  • Containers: A more lightweight form of virtualization where the application and its dependencies are packaged together, but they share the host OS kernel.
    • Benefit: Containers are much faster to start and use fewer resources than VMs.
  • VDI (Virtual Desktop Infrastructure): Hosting desktop operating systems on a centralized server. Users connect to their virtual desktops from thin clients or other devices.

āš ļø Common Pitfall: Not allocating sufficient physical resources (CPU, RAM, storage) to the host machine. Running multiple VMs can be very resource-intensive, and a lack of resources will lead to poor performance for all of them.

Key Trade-Offs:
  • Performance (Type 1) vs. Ease of Use (Type 2): Type 1 hypervisors are for production server environments. Type 2 hypervisors are for individual desktop use cases.

Reflection Question: Why are containers considered more "lightweight" and efficient than traditional virtual machines?