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.