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

In the field of vir­tu­al­iza­tion, 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 vir­tu­al­iza­tion.

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 vir­tu­al­iza­tion.

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, op­ti­miz­ing 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 vir­tu­al­iza­tion 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 spe­cial­ized 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 vir­tu­al­iza­tion 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, cen­tral­ized man­age­ment, which is carried out using Nutanix software.
• Citrix Hy­per­vi­sor: Formerly known as XenServer, this bare-metal hy­per­vi­sor is a component of Citrix’s vir­tu­al­iza­tion 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 vir­tu­al­iza­tion 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 vir­tu­al­iza­tion 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 uti­liza­tion and per­for­mance.
• Data centers and cloud in­fra­struc­tures: In data centers 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 vir­tu­al­iza­tion: Type 2 hy­per­vi­sors are an af­ford­able option for vir­tu­al­iza­tion. 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.