What’s the difference between type 1 and type 2 hypervisors?

In the field of virtualisation, hypervisors are central to running virtual machines. Both type 1 and type 2 hypervisors have their own strengths, weaknesses and typical use cases.

What is a hypervisor?

A hypervisor is a type of software that can run multiple virtual machines (VMs) on the same physical hardware. Hypervisors are also called virtual machine monitors (VMM) and manage resources such as CPU, memory and networks, and allocate the resources to VMs. With hypervisors, users can use VMs to run different operating systems, like Windows or Linux distributions, at the same time.

There are two types of hypervisors:

• Type 1 hypervisors
• Type 2 hypervisors

Type 1 and type 2 hypervisors share some similarities. Both can create multiple VMs on a single physical machine. They can also isolate virtual machines from each other, which enhances security and prevents problems occurring in one VM from affecting other VMs. Both types of hypervisors make it possible to start, stop and monitor VMs as well. Additionally, resources can be allocated and adjusted as needed. Users can typically manage VMs and allocate resources through a user interface or an API.

How are type 1 hypervisors different from type 2 hypervisors?

One main difference between type 1 hypervisors and type 2 hypervisors is that type 1 hypervisors don’t depend on an operating system to function. In the next two sections, we’ll take a closer look at the different characteristics of these two types of virtualisation.

Type 1 hypervisor

A type 1 hypervisor, also referred to as a bare-metal hypervisor, runs directly on physical hardware. With this type of hypervisor, the hypervisor is the first layer of software that is loaded onto the PC or server. It acts as an intermediary between the hardware and the virtual machines (VMs). This type of architecture provides a particularly powerful and efficient solution for virtualisation.

Thanks to their direct access to physical resources, Type 1 hypervisors have low latency and a fast response time. They can allocate CPU cores, memory and network interfaces efficiently and precisely, optimising the performance of virtual machines. They also ensure strong isolation between virtual machines, increasing the security and stability of the entire virtual environment.

Type 1 hypervisors often come with features such as live migration, where VMs can be moved from one physical machine to another while they are running. Many type 1 hypervisor providers also support high availability and disaster recovery. Type 1 hypervisors are also often equipped with interfaces for automation and control, for example, with APIs or special management tools.

Type 2 hypervisor

A type 2 hypervisor, or hosted hypervisor, is a virtualisation technology that runs as an application on an operating system (host OS). Type 2 hypervisors act as a layer between the host operating system and VMs, with the VMs running as processes or threads within the host OS. The hypervisor is able to profit from the host OS’s drivers and services, often making the setup process simple. The VMs can often host different guest operating systems such as Windows, Linux or other specialised systems.

Type 2 hypervisors access hardware resources through the host OS, which means they have to share physical resources with the host system. This can lead to performance degradation, especially if the host OS is heavily loaded or there are lots of processes running simultaneously. One benefit that type 2 hypervisors have over type 1 hypervisors is their compatibility with existing hardware and software infrastructure, which makes deploying and integrating them into an established IT environment easier.

Type 2 hypervisors typically offer a graphical user interface or dashboard for setting up and managing virtual machines. With type 1 hypervisors, this is not always the case. In the dashboard, users can conveniently create, configure and start VMs as well as dynamically adjust resources such as CPU, RAM and storage.

Examples of type 1 hypervisors

• KVM: a KVM (Kernel-based virtual machine) is a bare-metal hypervisor that is integrated into the Linux kernel. As such, it offers high performance and flexibility in Linux environments. It is also a common component of many modern virtualisation and cloud infrastructures.
• Nutanix AHV: Nutanix AHV (Acropolis Hypervisor) is a type 1 hypervisor that runs as a core element in the Nutanix hyperconverged infrastructure (HCI). AHV stands out with its excellent performance and easy, centralised management, which is carried out using Nutanix software.
• Citrix Hypervisor: formerly known as XenServer, this bare-metal hypervisor is a component of Citrix’s virtualisation infrastructure. Citrix Hypervisor comes with integrated security features to prevent attacks and ensure guest operating systems are isolated.

Examples of type 2 hypervisors

• VirtualBox: Oracle’s VirtualBox is a hosted hypervisor that is installed as an application on an operating system like Windows, macOS or Linux. VirtualBox is known for its user-friendliness and flexibility.
• Parallels Desktop: Parallels supports guest operating systems like Windows, Linux and other versions of macOS. You can place applications from virtual machines directly in the dock and easily exchange files and data between macOS and virtual machines using drag and drop.
• QEMU: QEMU is an open-source virtualisation platform that can emulate different CPU architectures. This gives users the possibility to create and run virtual machines with various architectures, such as an x86 on ARM hardware or vice versa.

When to use type 1 hypervisors and when to use type 2

When choosing between a type 1 and type 2 hypervisor, you should consider the specific requirements of your virtualisation environment. Both types of hypervisors offer their own advantages and are suitable for different use cases.

Use cases for type 1 hypervisors

• Large-scale enterprise environments: type 1 hypervisors are particularly suitable for companies that want to run a large number of virtual machines on servers. Having direct control over the hardware promotes better resource utilisation and performance.
• Data centres and cloud infrastructures: in data centres where many virtual machines are running, type 1 hypervisors are the preferred choice because they offer high performance and stability. Features such as live migration and high availability are especially important here.
• High security requirements: compared to type 2 hypervisors, type 1 hypervisors have fewer software components, resulting in a smaller potential attack surface. The architectures of type 1 hypervisors means that they are also able to provide better isolation between virtual machines (VMs).
• Performance-intensive workloads: programs that require high performance, such as databases, machine learning applications and big data, benefit from the fact that type 1 hypervisors make it possible to directly control the hardware.

Use cases for type 2 hypervisors

• Development and test environments: type 2 hypervisors are ideal for developers that want to test different operating systems and apps on the same hardware. Type 2 hypervisors offer a quick and easy way to create and manage virtual machines.
• Trainings: hosted hypervisors are great for workshops and trainings. Users can safely explore and experiment with different operating systems and applications, knowing that the actions they take won’t pose any risks to the hardware or the host operating system.
• Personal use: type 2 hypervisors are convenient for personal use and small projects. Users can run operating systems and applications on their own computers without the need for additional hardware or complex configurations.
• Affordable virtualisation: type 2 hypervisors are an affordable option for virtualisation. You don’t need any special type of hardware to use them. You can often use them for free or purchase the software for a relatively low price.