What are Virtual Machines (VMs)?

Virtual Machines (VMs) are the most common form of compute resource in Infrastructure as a Service (IaaS) cloud environments.

They are essentially software-based computers that run on physical hardware.

Definition:

• A Virtual Machine (VM) is a virtualized instance of a computer system.
• It behaves like a physical computer, with its own operating system (OS), CPU, memory, storage, and network interface, all running on a shared physical server.
• Each VM is isolated from other VMs on the same host, allowing multiple independent "computers" to run concurrently on a single piece of hardware.

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Key Components of a VM:

• Virtual CPU (vCPU): Virtualized processing power allocated from the host's physical CPU.
• Virtual Memory (vRAM): Virtualized RAM allocated from the host's physical memory.
• Virtual Disk: A file on the host's physical storage that acts as the VM's hard drive.
• Virtual Network Interface Card (vNIC): Allows the VM to connect to a virtual network.
• Guest Operating System: The OS installed within the VM (e.g., Windows Server, Linux, macOS).

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Customer Control & Management: When you provision a VM in the cloud (typically an IaaS offering), you are responsible for managing everything inside that virtual machine. This includes:

• Installing, configuring, and patching the Guest Operating System.
• Installing and managing all applications and software.
• Managing data stored on the VM's virtual disks.
• Configuring network settings within the VM (e.g., IP addresses, firewall rules specific to the OS). The cloud provider handles the underlying physical server, the hypervisor, and the physical network.

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Analogy: A Computer within a Computer

Imagine you have a powerful laptop (the physical host machine).

Now, picture installing a special software that allows you to run another entirely separate operating system (like a Windows PC on your Mac, or a Linux machine on your Windows PC) right within your laptop, complete with its own files, programs, and settings.

• Your Laptop: The physical server (host machine).
• The Special Software: The hypervisor.
• The Separate OS You Run: The Virtual Machine (VM). You can use both your main laptop OS and the VM simultaneously, and what happens in one doesn't directly affect the other.

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Use Cases:

• Hosting Web Servers and Applications: Running websites, e-commerce platforms, and enterprise applications.
• Development and Testing Environments: Quickly spinning up isolated environments for developers to test code without affecting production systems.
• Migrating On-Premises Workloads (Lift-and-Shift): Moving existing applications and servers from a traditional data center to the cloud with minimal changes.
• Running Legacy Applications: Hosting older software that requires specific operating systems or configurations not supported by newer hardware.
• Database Servers: Running relational or NoSQL databases that require dedicated compute resources.

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Quick Note: The "Workhorse" of IaaS

• VMs are the workhorses of Infrastructure as a Service (IaaS).
• They offer robust isolation and a familiar computing environment, making them ideal for traditional applications and for organizations that require significant control over their operating systems and software stack in the cloud.