What is a Hypervisor?

Hypervisors began in the 1960s for mainframe computers. IBM used them for research and experiments. In the 1990s, VMWare used them for industry-standard servers and commercial purposes. Later on, Linux and Unix systems began using them around 2005. The benefits of increased computing power made hypervisors more popular among IT practitioners. 

But what are hypervisors, and why have they become essential to IT? 

Let’s find out.

Table of Contents

This article will cover the following topics:

1. Hypervisor Defined
2. How Hypervisors Work
3. Installing a Hypervisor
4. Benefits of Hypervisors
5. Hypervisor Challenges
6. Hypervisor Security Best Practices
7. Types of Hypervisors
8. Type 1 vs. Type 2 Hypervisors
9. Uses of Hypervisor Type1 versus Type 2
10. Summary

1. Hypervisor Defined

A hypervisor is software running multiple Virtual Machines (VMs) simultaneously on a single physical machine.

2. How Hypervisors Work

Imagine managing 50 apartment units, each leased to different tenants. Ensuring that each unit has a reliable water supply and electricity could be quite a challenge, right? Now, picture all those apartment units housed in a single condominium building. While each tenant’s privacy is maintained, they share the building’s overall water and electricity resources. Wouldn’t managing the water supply and electricity of those 50 units be much easier? 

This concept is similar to how a hypervisor works in the world of computing. As a building administrator allocates the building’s shared resources, the hypervisor distributes the physical machine's resources, such as memory and CPU, among the virtual machines as needed, so each machine can work independently. The hypervisor works like an “operator” that enables several machines to share one physical computer's resources.

Although the hypervisor facilitates communication among VMs, it also ensures that VMs are isolated from each other, ensuring that no other VM is affected when one of them encounters a problem.

3. Installing a Hypervisor

The hypervisor software must be installed on physical servers to enable virtualization, supporting cloud transformation initiatives with minimal disruption to operations.

Once installed, the host server or machine allows one or more guest or virtual machines (VMs) to operate independently. The virtualization software combines the host’s hardware resources and allocates them to the individual VMs, enabling them to function separately in a self-contained environment.

Here are a few examples of popular Hypervisors and how to install them: 

1. VMware ESXi

VMware ESXi is a Type 1 hypervisor (bare-metal). Popular use cases include enterprise-grade server virtualization.

How to install it?

• Download the ESXi ISO, create a bootable USB, and boot the server from it.
• Follow the on-screen installer, configure the network, and set a root password.

2. Microsoft Hyper-V

Microsoft Hyper-V is a Type 1 hypervisor (bare-metal or hosted). Popular use cases include virtualization for Windows environments.

How to install it?

• On Windows Server, use Server Manager to add the “Hyper-V” role.
• Reboot the system, configure the virtual switch, and create VMs via Hyper-V Manager.

3. Oracle VirtualBox

Oracle VirtualBox is a Type 2 hypervisor (hosted). Popular use cases include desktop virtualization, testing, and development.

How to install it?

• Download VirtualBox, run the installer, and complete the setup wizard.
• Launch VirtualBox and create virtual machines.

4. KVM (Kernel-based Virtual Machine)

KVM Project is a Type 1 hypervisor (integrated into the Linux kernel). Popular use cases include open-source virtualization for Linux environments.

How to install it?

• Install KVM and related packages (e.g., qemu-kvm and libvirt) on Linux.
• Use virt-manager (GUI) or virsh (CLI) to manage VMs.

4. Benefits of a Hypervisor

Do organizations need hypervisors, or can they do without them? Hypervisors provide several key benefits that make them essential for modern IT infrastructure. These advantages include the following:

1. Efficiency A hypervisor eliminates the need for tedious manual installation of operating systems and related software, allowing a more efficient creation of virtual environments. For example, an employee can replicate their desktop on a server, providing them with remote access to their work files and applications from anywhere.
2. Quick Failure Recovery Its ability to create backup copies enables quick failure recovery, as it captures images of the VM’s details, including instructions on installation and configuration, which can be used for VM restoration. The VM can also be moved to another host to restore it.
3. Hardware Independence Hardware independence refers to the ability to run on different hardware types or transfer virtual servers to other virtualization hosts. VMs can operate on various types of physical hardware, which means the configuration, deployment, and management of software applications need not be constrained by the hardware setup.
4. Reduced Capital Expenditure Integrating VMs into a single physical service decreases the need for additional servers. With fewer servers used, an organization can cut down on power consumption, leading to a reduction in energy costs. Likewise, the space needed to house the servers will be diminished significantly.
5. Legacy System Support Sometimes, organizations invest a hefty amount in software. When the necessary components to operate it, such as the CPU, become obsolete, investing in modern and more expensive software seems imperative. Using a hypervisor presents a better alternative because it allows the continued use of the software through virtualization.
6. Resource optimization An organization may have idle resources when each branch or department operates on individual physical servers. A hypervisor can consolidate the functions of these servers into a single machine, even if they run on different operating systems and program elements. A hypervisor also maximizes the use of hardware resources and facilitates scalability.

5. Hypervisor Challenges

Hypervisors offer several benefits, but using them also poses some risks. Some disadvantages are covered in the Type 1 versus Type 2 Hypervisor section. This section will cover two major challenges. 

a. Resource Contention

Resource contention, sometimes called deadlock, refers to a conflict over the resources shared by many VMs. These resources include, but are not limited to, cache memory, disk storage, external network devices, internal buses, and RAM. This challenge occurs as multiple VMs compete for physical resource allocation, which results in a bottleneck. Resource contention happens when two or more VMs want access to the same resource or wait for another VM to release a resource.

The key is proper management and distribution of virtual resources to ensure all VMs in the shared model get their fair share of resources.

b. Security Risks

Hypervisors are vulnerable to security risks despite the isolation layer they provide because they control and manage all the hardware resources of the VMs residing on them.  If a hypervisor is threatened with a cyberattack, the security of multiple VMs is likewise threatened. This may lead to serious data breach cases or, worse, a system collapse.

Implement security controls for the hypervisors and the virtual environments they manage. Recognize and understand the existing vulnerabilities to enable better management of security risks. Follow industry guidelines on virtualization security. Plan your IT network carefully to mitigate the risks. Adopt best practices on hypervisor security.

6. Hypervisor Security Best Practices

Keeping hypervisors secure is crucial to the security of virtual environments. Adopting and sticking to the best hypervisor security practices diminishes risk exposure, increasing the virtual environments’ integrity. In this section, we will go through four of the most important Hypervisor security best practices. 

1. Access Restriction Adopt a role-based access control (RBAC) system so that only those who need and can be trusted to access the hypervisor are authorized to do so. This should reduce any insider threat or breach from external partners.
2. Activity Monitoring Always monitor hypervisor activities proactively to prevent security threats and address these threats promptly.
3. Network Segmentation Configure network boundaries for different VMs to control traffic flow between them and reduce the attack space.
4. Regular Patching Regular and proper patching of the hypervisor shields it from potential threats, reducing the risks of security breaches.

7. Types of Hypervisors

Hypervisors are categorized into two main types: Type 1, or bare metal hypervisor, and Type 2, the hosted hypervisor. 

The more common Type 1 hypervisors include VMware vSphere/ESXi, Microsoft Hyper-V, Kernel-Based Virtual Machine (KVM), Red Hat Enterprise Virtualization, and Xen/Citrix Xen/Server. For hosted hypervisors, the common examples include VMware Fusion, Parallels Desktop, and CentOS Virtualization.

The image below shows the difference between Type 1 versus Type 2 Hypervisor.

Let’s take a look at the advantages and disadvantages of each type.

8. Type 1 vs. Type 2 Hypervisor

Type 1 hypervisor is also known as bare metal hypervisor because it is installed directly on the physical hardware where the operating system is installed. A Type 2 hypervisor, on the other hand, is so-called because it is installed as a software application on a host operating system. Let’s compare Type 1 vs. Type 2 hypervisors considering complexity, cost, efficiency, manageability, performance, scalability, and security.

a. Complexity

Generally, Type 1 hypervisors are more complex than Type 2 hypervisors. Bare metal hypervisors need an external device with a browser, unlike hosted hypervisors, which can operate on standard desktops or laptops. They are also limited by hardware compatibility, which means Type 1 hypervisors can only work on specific hardware components identified from vendors’ approved lists.

b. Cost

Type 1 hypervisor is more expensive than Type 2 because of its need for dedicated hardware and special management tools and its installation challenges.
For example, a one-year subscription for a VMWare Type 1 hypervisor kit, inclusive of a management program, has a base price of $1,268.

Because hosted hypervisors run on a wider range of operating systems and software environments, Type 2 hypervisors are considered more cost-effective. Some Type 2 hypervisors are open-source, meaning they come for free. However, if you avail of this hypervisor type through a vendor, they may charge you for the license or any other special feature you would like to add.

c. Ease of Installation

When it comes to installation, Type 2 hypervisors are easier to install than Type 1 hypervisors. Hosted hypervisors may be installed using common OS interfaces and tools and by somebody with zero to basic technical knowledge. Bare metal hypervisors require a high level of technical knowledge required of a systems administrator.

Installing and configuring bare metal hypervisors can be difficult. A Type 1 hypervisor may require extra steps to install if it does not support the type of hardware and applications available. These additional steps translate into more man-hours and therefore, higher labor costs. IT staff may need to undergo further training to speed up the installation process, but even that will incur cost.

d. Efficiency

Type 1 hypervisors interact directly with the hardware resources, allowing them to run several VMs more efficiently than Type 2 hypervisors can. Bare metal hypervisors can develop their resource allocation strategies, but hosted hypervisors are constrained to the slower process of negotiating with the operating system.

e. Manageability

With bare metal hypervisors, monitoring all VMs and ensuring that the resources they need are adequately provided can be daunting. Another management challenge this hypervisor type poses is complying with licensing requirements. You must ensure that the software applications running in multiple VMs are all compliant.

Hosted hypervisors don’t need separate software to manage VMs, making them easier to manage.

f. Performance

Type 1 hypervisors perform better than Type 2 hypervisors because they do not have to go through the operating system layer, as a hosted hypervisor does. They have direct access to the host computers’ components such as storage space, RAM, and CPU.

Type 2 hypervisors are also limited to resources that the operating system can or is willing to provide. These hypervisors need to request hardware resources from the host operating system, slowing down their response time.

g. Scalability

Bare metal hypervisors are more scalable than hosted hypervisors. A Type 1 hypervisor’s direct access to the host machine’s hardware enables it to assign resources directly to VMs, optimize physical resources, and scale to large-volume workloads.

On the other hand, the hosted hypervisor’s dependence on hardware resources prevents it from scaling.

h. Security

Bare metal hypervisors manage guest operating systems and allocate resources to VMs directly to the hardware. Because they are separate from the operating system, which is susceptible to attacks, Type 1 hypervisors are more secure and stable. This level of security is enhanced by the base metal hypervisor’s ability to support software-defined storage and networking.

Type 2 hypervisors are less secure and stable because a security breach in one VM will affect the others. They are also more prone to vulnerabilities because of their dependence on the host operating system.

9. Uses of Type 1 Hypervisor vs. Type 2

Given the advantages and disadvantages of hypervisor Type 1 vs. Type 2, let us identify applications that suit each type.

1. Type 1 Hypervisor Type 1 hypervisors are ideal for organizations that need efficiency, peak performance, high-level scalability, and superior security. They will suit cloud computing environments, enterprise-level computing workloads, and large data centers.
2. Type 2 Hypervisor Organizations that are not resource-intensive or do not deal with business-critical workloads may benefit from the cost-effective and less complex Type 2 hypervisor. Hosted hypervisors, sometimes called client hypervisors, are best used for development, end-users and software testing, and personal use. They are also good for organizations that are after flexibility and a simple setup.

10. Summary

A hypervisor is software that lets you run multiple virtual machines (VMs) on one physical computer. It splits up resources like memory and CPU, so each VM works independently, even though they share the same hardware.

There are two types of hypervisors:

• Type 1 (Bare Metal): Directly installed on the hardware. It’s super-efficient, secure, and great for big tasks like cloud computing.
• Type 2 (Hosted): Runs on an operating system. It’s easy to set up, budget-friendly, and perfect for testing, development, or personal projects.

We cannot say that one type of hypervisor is better than the other. You just have to select which type is suitable for your needs. Knowing what these hypervisor types offer enables you to make informed decisions that help you achieve your virtualization goals.