Summary of "Lec 16: Introduction to Virtualization"

Introduction to virtualization

Virtualization is the foundational technology behind cloud computing. It allows a single physical machine to present multiple independent virtual machines (VMs), so many users or workloads can run concurrently while each user feels they have their own system.

Analogy: a single wall power socket vs. an extension box with multiple outlets — the physical resource is one, virtualized into many accessible points.

Core concept

One physical host can be partitioned into many virtual machines.
Each VM is independent and can run its own guest operating system and applications.
Virtualization hides the physical characteristics of resources (CPU, RAM, storage, network) from users.

How it works

A hypervisor (virtual machine monitor) is the primary software layer that enables virtualization. It runs on the host server/hardware and creates VMs.
The hypervisor allocates resources (CPU, RAM, storage, etc.) to each VM and enforces isolation between VMs.
VMs can run different guest operating systems (Windows, Linux, macOS, etc.) on top of the host hardware without modifying the underlying physical machine.

Benefits

Better utilization of compute resources (reduces idle CPU/RAM/storage).
Lower physical hardware cost (multiple VMs per server).
Improved fault tolerance and easier failover (VMs can be migrated or shifted).
Reduced power and cooling needs (fewer physical machines).
Increased agility and productivity — rapid provisioning of environments and OS-specific applications.

Modes of virtualization

Full virtualization
- The hypervisor completely simulates hardware.
- The guest OS runs unmodified and is unaware it’s virtualized.
- Good for compatibility with unmodified guest OSes.
Paravirtualization
- The guest OS is modified to cooperate directly with the hypervisor.
- The guest is aware of virtualization and can achieve improved performance.

Practical / teaching points

Use-case: instead of replacing a host OS to run a different OS, create a VM on top of the existing host and install the desired guest OS and applications there.
Emphasis on isolation: each VM runs its own apps independently, with the hypervisor managing resource allocation and containment.