Nutanix Glossary

What is a Hypervisor?

April 20, 2022 | min

A hypervisor, also known as a virtual machine monitor (VMM), is a software layer that enables multiple virtual machines (VM) to run on a single physical machine. The hypervisor provides each virtual machine with a virtualised set of hardware resources, such as CPU, memory, storage, and network interfaces, which allows them to operate independently of each other and the host system. Hypervisors play an essential role in enabling server virtualisation, which is itself essential to enabling cloud computing.

Hypervisors are used in various settings, including datacentres, cloud computing, and desktop virtualization, to consolidate physical hardware, increase efficiency, and improve flexibility in managing resources.

what is hypervisor

Why use a hypervisor?

The primary technological problem that hypervisors solved was that most physical hardware could run only one operating system at a time. This constraint often led to wasted resources, as a single OS seldom fully utilised the hardware’s capacity.

Hypervisors address the above constraint by aggregating the resources of virtualised physical servers (such as memory, network bandwidth and CPU cycles) and then allocating those resources to virtual environments, called virtual machines. Hypervisors are also known as virtual machine monitors (VMM). A VM is essentially a software-based computer, with access to the same resources as a physical computer, including an OS and apps. However, a hypervisor lets you run multiple VMs as guests, thereby using the physical resources of the underlying host machine much more efficiently. Each VM can act as a dedicated machine for every service, app or operating system, allowing you, for example, to run multiple different OSs on a single server. The hypervisor also separates the VMs logically, which protects each individual VM against the effects of problems with other individual VMs on the same hypervisor, such as crashing, errors, or security attacks.

Top 10 benefits of hypervisors

Some of the benefits of using a hypervisor include:

  1. Server consolidation: Hypervisors allow multiple virtual machines to run on a single physical server, which can lead to significant cost savings by reducing the number of physical servers required.

  2. Increased efficiency: With hypervisors, administrators can more efficiently allocate resources like CPU, memory, and storage to virtual machines, which can lead to better overall system performance.

  3. Improved security: Virtual machines are isolated from each other, which can help prevent security breaches and protect against malware attacks.

  4. High availability: Hypervisors can provide high availability features such as live migration, which enables virtual machines to be moved from one physical server to another without downtime.

  5. Disaster recovery: Hypervisors make it easier to implement disaster recovery plans by allowing virtual machines to be replicated and moved between physical servers.

  6. Flexibility: Virtual machines can be created, configured, and deleted quickly and easily, providing administrators with greater flexibility in managing resources.

  7. Scalability: Hypervisors can scale up or down as needed, allowing administrators to add or remove virtual machines based on changing business needs.

  8. Cost savings: Hypervisors can reduce hardware costs, energy costs, and maintenance costs by consolidating servers and improving resource utilisation.

  9. Testing and development: Hypervisors can be used to create virtual test environments, which can reduce the need for physical hardware and speed up the development process.

  10. Simplified management: Hypervisors provide a centralised management interface for all virtual machines, making it easier for administrators to monitor and manage the entire virtualised environment.


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Types of hypervisors

Type 1 hypervisor (also known as a bare-metal hypervisor)

Type 1 hypervisors are installed directly on the physical server, which is why they are also called “bare metal” hypervisors. Direct access to the resources of the physical server makes Type 1 hypervisors highly efficient. This design also makes Type 1 hypervisors more secure, as it limits the attack surface and potential for compromise. Type 1 hypervisors are by far the most common choice within enterprise IT contexts, primarily due to their strong security, scalability, stability, and performance. Examples of the most widely used hypervisors include Nutanix AHV, VMware ESXi, Microsoft Hyper-V, and Citrix Hypervisor.

Type 2 hypervisor (also known as a hosted hypervisor)

Type 2 hypervisors differ in that they run as applications on a physical server’s preexisting OS. Because they run on the host OS, which sits between the physical server and the hypervisor, they are also known as “hosted” hypervisors. Type 2 hypervisors are not ideal for server-based environments, given that they have a higher latency and risk exposure than Type 1. They are, however, relatively easy to install, and can work well in specific use cases, such as individual PC users who need to run more than one operating system, and where performance and security are not principal concerns.

Hypervisor security considerations 

When it comes to hypervisor security, there are several key considerations that organizations must keep in mind. First, it's important to understand that hypervisors can introduce security risks. As such, it's important to apply security best practices when configuring and managing hypervisors. This includes using strong authentication and access controls, implementing network segmentation to isolate virtualized environments, and restricting access to hypervisor management interfaces to authorized personnel only. It's also important to regularly patch and update hypervisors and guest operating systems to address any security vulnerabilities that may be discovered. Finally, organizations should consider using tools such as intrusion detection systems and security information and event management (SIEM) solutions to monitor their virtualized environments and detect any potential security threats. By taking these considerations into account, organizations can help ensure the security of their virtualized environments.

Hypervisor security best practices:

  1. Keep hypervisor software up-to-date: Regularly patch and update the hypervisor software to ensure it is free of vulnerabilities.

  2. Harden hypervisor configuration: Configure the hypervisor to comply with security best practices, disable unnecessary services, and apply appropriate access controls.

  3. Isolate management interfaces: Keep management interfaces separate from other networks to prevent unauthorised access.

  4. Use secure authentication: Use strong passwords, two-factor authentication, and other authentication methods to prevent unauthorised access to the hypervisor.

  5. Implement network security: Use firewalls, intrusion detection and prevention systems, and other security measures to secure network traffic to and from the hypervisor.

  6. Monitor hypervisor activity: Monitor and log hypervisor activity to detect and respond to security incidents.

  7. Implement virtual machine security: Use security features such as encryption, access controls, and firewalls to secure virtual machines running on the hypervisor.

  8. Limit hypervisor access: Limit access to the hypervisor to authorised personnel only, and ensure that access is granted on a need-to-know basis.

  9. Conduct regular security audits: Conduct regular security audits to identify potential vulnerabilities and ensure that security controls are effective.

Top considerations when selecting a hypervisor

  • Performance and scalability: Hypervisors should be able to handle the workload requirements of the organisation, including the ability to scale up or down as needed to accommodate changing demands.
  • Features and capabilities: Different hypervisors offer different features and capabilities, so organizations should choose a hypervisor that meets their specific needs, such as support for specific operating systems, virtualization types, and management tools.
  • Cost: Different hypervisors come with different costs, including licensing fees, support costs, and hardware requirements. Organisations should choose a hypervisor that provides the necessary features and capabilities at a cost that fits within their budget.
  • Compatibility: Organizations should ensure that the hypervisor they choose is compatible with their existing hardware and software infrastructure, including server hardware, storage systems, and networking equipment.
  • Security: Hypervisors should have robust security features and be able to support secure virtualization environments, including isolation and segmentation of virtual machines.
  • Support and maintenance: Organizations should choose a hypervisor with a reliable vendor that provides timely and effective support and maintenance services.
  • Ecosystem: Does it support a rich ecosystem? For example, does it support the most widely used guest operating systems? Microsoft, Suse, RedHat, Ubuntu, CentOS. Does it support leading enterprise apps and technologies such as Microsoft SQL Server, Exchange, SAP, Oracle, Citrix, Splunk, SAP, and VMware Horizon?

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