Virtualization and Hypervisors Overview

Virtualization

• Virtualization is a technique that allows multiple guest operating systems (OS) to share a single piece of hardware, such as a server.
• The underlying virtualization software layer is called the host system.
• A guest operating system is an OS hosted by the host system.

Hypervisor

• A hypervisor is software or firmware that enables the segmentation and monitoring of physical hardware.
• Two types of hypervisors exist: Type 1 and Type 2.

Type 1 Hypervisor

• Runs directly on the system's hardware.
• No intermediary operating system is required.
• Examples include ESXi, Proxmox, and Hyper-V.
• "Bare metal" environment means the virtual machine is installed directly on the hardware rather than within the host operating system (OS).
• "Bare metal" usually refers to the hard drive, where the OS is normally installed.

Type 2 Hypervisor

• Runs as an application within an operating system environment.
• Examples: VMware Workstation, Oracle's VirtualBox.
• The host hardware is the base for the host OS, which supports the virtualization application.
• The virtualization application, in turn, hosts guest OS(s).

Reasons to Use Virtualization

• Hardware underutilization
• Data centers running out of space
• Increasing energy costs
• Rising system administration costs.
• Setting up complex testing environments, including networking
• Faster access to other operating systems
• Virtual machine running alongside the host operating system, without shutting down the host.
• Access to other operating systems quickly.
• Snapshots and undo disks for software updates on a VM
• Virtualized hardware allows easier driver access for older operating systems using modern hardware
• VM's often have more widely supported virtual hardware than older hardware that is independent of a host operating system.

Benefits of Virtualization

• Shorter development cycles
• Increased hardware utilization
• Reduced problem-resolution time
• Increased productivity
• Accelerate time-to-market
• Improved project quality
• Relocation of systems from one machine to another, if needed
• Disaster protection in case of hardware failure

What Can Be Virtualized

• Network: Dividing network bandwidth into separate independent channels, and virtualizing routers (including NAT and DHCP functionality).
• Storage: Separating virtual machine storage areas, pooling physical storage from various network storage devices (like SAN - Storage Area Networks) into a singular device.
• CPU: Using similar, but independent technologies by Intel (VT-x) and AMD (AMD-V), to improve processor performance by translating instructions and memory addresses, common challenges for virtualization.

Licensing

• Licensing for software is important for all scenarios, and especially important when using software in a virtualized environment, including Operating Systems (OS).
• Licenses for Windows virtual machines need licensing for both their use as guest operating system and as the host.
• Apple operating systems may require that the virtual hardware for the Mac OS is Apple-compatible to run in a virtual environment.
• Open-source licensing may differ for each Linux distribution. Always check before proceeding.

This quiz covers the fundamentals of virtualization, including the concepts of host systems and guest operating systems. It delves into the two types of hypervisors: Type 1 and Type 2, highlighting their differences and providing examples of each type. Test your knowledge on these essential components of virtual technology.