Hypervisors

What is a Hypervisor: A Brief Overview

A hypervisor, also known as a virtual machine monitor (VMM), is a software, firmware, or hardware piece that allows running multiple virtual machines, each with separate operating systems, simultaneously on a host system.

Origins & Definition of Hypervisors

The term Hypervisor originated from the word 'supervisor'. The 'hyper' prefix was adopted to represent the one level higher than a supervisor. In terms of definition: Hypervisors were developed to efficiently utilize computer resources and to handle the increasing data processing requirements of complex applications.

Hypervisors in Modern Computing

In the present day, Hypervisors play a pivotal role in cloud computing, datacentres, and where server consolidation is needed. They are optimized to manage multiple virtual machines effectively.

The Key Functions and Importance of Hypervisors

A hypervisor does more than just allowing multiple virtual machines on a single host. The list points below highlight some of its other critical functions:

• Manages the virtual machines' resources
• Ensures that each virtual machine is isolated from others
• Allocates necessary resources to each virtual machine
• Starts and shuts down virtual machines as required
• Ensures the effective and fair distribution of CPU, memory, and other resources

Role of Hypervisor in Computer Science

The application of Hypervisors in the realm of computer science is wide and varied. Below is an example of some common utilizations.

Physical Server - Disk Storage - Hypervisor - Operating System - Apps

In the configuration above, the Hypervisor controls access to physical resources, and provide a consistent platform for the operating system to run on different hardware configurations.

Hypervisor Use Cases Across Different Fields

Hypervisors have found widespread use, not just in IT infrastructure, but also in various other fields. A few examples are:

• In the automotive industry, Hypervisors are used to isolate the infotainment systems from the critical systems for safety purposes.
• In the financial sector, Hypervisors allow for the maintenance of legacy systems alongside newer systems.
• In Scientific Research, Hypervisors allow for simulations and analyses to be run on isolated systems, avoiding any risk to the primary research data.

The Different Types of Hypervisors

As we delve further into the world of hypervisors, it's important to note that there are two distinct types of hypervisors – Type 1 and Type 2. These vary in the way they interact with the host system and the virtual machines.

Type 1 Hypervisor: An In-depth Review

Type 1 Hypervisors, also known as "native" or "bare metal " hypervisors, are installed directly onto the host hardware. This direct link to the hardware, without the intermediary of an operating system, offers several benefits. For starters, the absence of a separate OS layer minimises latency. Through direct control of hardware resources, Type 1 Hypervisors enable you to maximise performance.

Features and Utilities of Type 1 Hypervisor

Type 1 Hypervisors are extensively used in enterprise environments, and their features are closely aligned with this usage:

• High Performance: Without the overhead of a host operating system, Type 1 Hypervisors can directly manage and allocate hardware resources for optimum performance.
• Superior Isolation: Each virtual machine operates independently. Consequently, if one machine encounters a problem, the others remain unaffected. This feature makes Type 1 Hypervisors highly suitable for mission-critical applications.
• Compatibility: Given their direct interaction with hardware, Type 1 Hypervisors can efficiently manage a wide array of hardware configurations and types.
• Security: The absence of a host OS also ensures that any potential vulnerability within the OS doesn't impact the hypervisor or the virtual environments running on it.

Common Examples of Type 1 Hypervisor

There are a number of widely used Type 1 Hypervisors with varying features and specialisations. Here's a rundown of a few noteworthy ones:

Type 2 Hypervisor: A Comprehensive Analysis

Moving on to Type 2 Hypervisors, these are often referred to as "hosted" hypervisors as they are installed on top of the host system's operating system, not directly on the hardware.

Essential Features of Type 2 Hypervisor

• Simplicity and Ease of Use: Due to their resemblance to traditional applications running on an operating system, Type 2 Hypervisors are generally easier to set up and manage.
• Compatibility: Given that they run as software on an operating system, Type 2 Hypervisors can run on a broader range of hardware - provided the host operating system supports it.
• Integration: As they live on the host OS, Type 2 Hypervisors can integrate closely with the operating system, which may result in better support for some peripherals and devices.

Common Usage of Type 2 Hypervisor

Examples of Type 2 Hypervisors include VMware Workstation, Oracle's VirtualBox, and Parallels. These solutions are often used by developers for testing software across multiple operating systems on a single physical computer.

Hypervisor and Virtual Systems

In the realm of computer science, Hypervisors and virtual systems are interconnected. The relationship is based on the fact that hypervisors facilitate virtualisation, and virtual systems make use of this feature to function optimally. To understand this dynamic, let's delve deeper into how these technologies interact.

The Interplay between Virtual Systems and Hypervisors

The nexus between hypervisors and virtual systems is of great consequence in understanding the paradigm of modern computing. Hypervisors serve as crucial elements that create the platform that allows these virtual systems to run. Without hypervisors, virtual systems could not exist. Hypervisors provide the environment, called a virtual machine (VM), in which an operating system can run. These VMs, in essence, mimic the functionality of a physical computer. They have simulated versions of fundamental elements like CPU, memory, and disk storage. Given their role, it is crucial to understand two key features of Hypervisors, which are Virtual Machine Isolation and Virtual Machine Inspection.

• Virtual Machine Isolation: Hypervisors are responsible for maintaining boundaries between different virtual machines. Each VM operates in isolation, and issues that occur within one VM do not affect others. This scenario is true even when many VMs share the same hardware resources.
• Virtual Machine Inspection: Hypervisors can examine the state of a virtual machine. This ability helps in identifying when a VM is idle and not utilising resources, and the hypervisor reassigns these resources to other VMs to optimise resource utilisation.

How Hypervisors Facilitate Virtual Systems

Hypervisors create and control virtual machines, thus making virtual systems possible. With a hypervisor in place, here's how a typical system setup looks:

Physical Server → Disk Storage → Hypervisor → Virtual Machine → Operating System → Applications

In this setup, the hypervisor controls access to the physical resources of the machine and provides a consistent platform for the virtual system to operate on. In order to manage a virtual system effectively, hypervisors perform several operations:

1. VM Allocation: Hypervisors allocate the physical server resources to different virtual machines.
2. VM Scheduling: The hypervisor decides which VM accesses the CPU based on scheduling algorithms.
3. VM Execution: Evaluating each instruction in a VM, the hypervisor decides whether to execute or hold it.
4. VM Management: The hypervisor also manages the start, pause, and stop operations of each VM.

The Impact of Hypervisors on Virtual Systems Efficiency

The efficiency of a virtual system directly corresponds to the efficiency of the hypervisor. Hypervisors boost efficiency by maximising server usage. Physical servers often remain largely underutilised, with some studies showing average server utilisation rates of around 15%. With hypervisors, several virtual systems can run on a single server, thereby ramping up server utilisation and cutting down on server costs. In addition, hypervisors also contribute to a reduction in power usage, cooling requirements, and server maintenance costs. They allow for streamlined software deployment processes, as software can be installed or updated on one VM, and the changes can quickly replicate to other VMs.