15.1 Processors, Parallel Processing and Virtual Machines

Objective: Show understanding of the concept of a virtual machine

A virtual machine (VM) is essentially a software-defined emulation of a physical computer system. It allows you to run an operating system and applications within a virtualized environment, as if it were a separate physical machine. This provides numerous benefits, including resource isolation, flexibility, and efficient hardware utilization.

What is a Virtual Machine?

Think of a virtual machine as a computer within a computer. It has its own virtual hardware, including a virtual CPU, memory, storage, and network interface. This virtual hardware is created and managed by a piece of software called a hypervisor.

A hypervisor is responsible for allocating the host machine's physical resources to the virtual machines. It ensures that each VM operates independently and doesn't interfere with other VMs or the host operating system.

Types of Virtual Machines

There are two main types of virtual machines:

• Type 1 Hypervisor (Bare-metal): This type of hypervisor runs directly on the hardware, without a host operating system. Examples include VMware ESXi and Microsoft Hyper-V (when installed directly on the hardware).
• Type 2 Hypervisor (Hosted): This type of hypervisor runs on top of an existing operating system. Examples include VMware Workstation and Oracle VirtualBox.

How Virtual Machines Work

1. Hardware Resources: The physical computer's resources (CPU, RAM, storage, network) are shared among the VMs.
2. Hypervisor Layer: The hypervisor sits between the hardware and the VMs. It manages the allocation of resources to each VM.
3. Guest Operating System: Each VM runs its own guest operating system, which is isolated from other VMs and the host OS.
4. Applications: Applications run within the guest operating system, as if they were running on a physical machine.

Benefits of Using Virtual Machines

Benefit	Description
Resource Optimization	Allows multiple operating systems and applications to run on a single physical machine, improving hardware utilization.
Isolation	VMs are isolated from each other and the host operating system, enhancing security and stability. If one VM crashes, it doesn't affect others.
Flexibility and Portability	VMs can be easily created, copied, and moved between different physical machines. This is useful for development, testing, and disaster recovery.
Cost Savings	Reduces the need for physical hardware, leading to lower capital and operational costs.
Testing and Development	Provides isolated environments for testing software and configurations without affecting the main system.

Use Cases for Virtual Machines

Virtual machines are widely used in various scenarios:

• Server Virtualization: Consolidating multiple physical servers into fewer, more powerful physical servers running VMs.
• Desktop Virtualization: Running desktop operating systems within VMs, allowing users to access their desktops from anywhere.
• Software Development and Testing: Creating isolated environments for developing and testing software.
• Disaster Recovery: Creating backups of VMs that can be quickly restored in case of a system failure.
• Running Incompatible Software: Running older operating systems or applications that are not compatible with the host OS.

Diagram of a Virtual Machine Setup

In summary, virtual machines are a powerful technology that provides a flexible, efficient, and secure way to run multiple operating systems and applications on a single physical machine. Understanding the concept of a VM and the role of a hypervisor is crucial in modern computing.