Nutanix Glossary

What is a Hypervisor?

December 18, 2023 | min

What is a hypervisor?

A hypervisor is a software that enables the creation and management of virtual machines (VMs) and allocates the host server’s compute, storage, and networking resources as needed by each VM. Hypervisors are crucial in enabling server virtualisation, a fundamental component of cloud computing. In a broader sense, virtualisation refers to the use of software to simulate or emulate physical resources. The hypervisor abstracts and isolates the VMs and their programs from the underlying physical server hardware, allowing a more efficient utilisation of physical resources, simpler maintenance and operations, and cost reduction.


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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.

Benefits of hypervisors

  • Speed, agility, and scalability – Organisations are no longer have to provision new environments each time a customer makes a request or when a developer requires a testing environment. Virtualisation makes it simple and fast to spin up new VMs and get them running whenever they’re needed. Given that each server can manage many virtual machines, scaling is also easy. 

  • More efficient utilisation of servers – Hypervisors ensure the optimal utilisation of a server's resources. Prior to virtualizsation and hypervisors, it was typical for an organisation to run multiple servers, each utilising less than half of its available resources.

  • Increased security – Even though a physical host server might be running numerous virtual machines, each VM is kept isolated from the others. That is advantageous if an attacker finds entry into one of the server’s VMs because the attacker won’t automatically be able to infiltrate other VMs on that server through the hypervisor. 

  • Portability and workload balancing – Separating the operating systems and applications of VMs from the physical host simplifies the process of migrating a VM from one host to another without causing disruptions. IT also can allocate resources across multiple servers if required. 

  • Improved resilience – Hypervisors can also quickly and easily move VMs and reallocate resources if a node fails, which helps maintain high availability and increased uptime. 

  • Cost savings – Virtualisation allows organisations to cut down on capital expenditures (CapEx) by utilising numerous virtual machines on a single physical server, thereby decreasing the necessity for additional hardware. Additionally, minimising the physical footprint results in OpEx savings by reducing expenses related to electricity, cooling, and maintenance. 

  • Faster data recovery – In case data in a VM is compromised or infected by malware or an attack, some hypervisors allow organisations to recover the data from a snapshot instead of having to restore a full backup. 

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Types of hypervisors

Type 1 hypervisor

Type 1 hypervisors are installed directly on the physical server, which is why they are also called “bare metal” hypervisors. Having direct access to the resources of the physical server makes Type 1 hypervisors highly efficient. This design also enhances the security of Type 1 hypervisors, 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

Type 2 hypervisors differ in that they run as applications on a physical server’s preexisting operating system. 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 higher latency and risk exposure than Type 1. However, they are 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 primary concerns.

What is a cloud hypervisor?

Given the widespread adoption of cloud computing by organisations, it’s important to recognise the pivotal role that virtualisation and hypervisors play in the cloud. A cloud hypervisor oversees and controls the virtual machines running on physical servers in data centres owned by cloud providers. These hypervisors simplify the management of distributed workloads across cloud architecture, which often operate on a multi-tenant model, allowing multiple customers to use their own assigned portions of a single architecture. 

In the cloud, scalability is near infinite and organisations pay only for the resources they consume. Hypervisors allow these organisations to take advantage of the agility and speed of the cloud. Users can access data and applications in virtual environments but IT still retains control of the organisation’s applications and data. Hypervisors also make it easy to move workloads and applications to the cloud, which increases an organisation’s agility and efficiency.

Hypervisors vs containers

While there are notable similarities between hypervisors and containers, it is crucial to understand that they are distinct entities. They both enable virtualisation on some level and are widely used for for enhancing the speed and efficiency of modern applications. However, they achieve these objectives through different approaches.

For example, a hypervisor enables the creation of virtual machines with their own operating systems and applications, operating autonomously from the hosting physical servers. On the other hand, containers are packages of software that contain chunks of an application’s data and configurations. The containers make it possible for that application to run on any operating system. Where the hypervisor decouples the software environment from the physical foundation, containers decouple applications from specific operating systems.

Organisations use hypervisors and containers for different needs. Hypervisors are used to optimise the utilisation of physical servers, enabling the creation and management of multiple VMs per host. In contrast, containers are used in developing and deploying specific applications. Containers are ultra-portable and very lightweight, which helps make moving them around fast and easy.

Due to their ability to abstract elements of VMs and applications from physical hardware and operating systems, both hypervisors and containers play crucial roles in today’s most advanced IT architectures.

Hypervisor security best practices 

Ensuring the security of hypervisors is crucial for maintaining the overall security of virtualised environments. Here are some best practices for hypervisor security:

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

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

  • Isolate management interfaces - Keep management interfaces separate from other networks to prevent unauthorised access.

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

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

  • Monitor hypervisor activity - Monitor and log hypervisor activity to detect and respond to security incidents.

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

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

  • 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 - Assess the hypervisor's performance capabilities and scalability to ensure it will support your mission-critical applications. Check out the benchmarks for performance in production (as close to real-world conditions as possible).
  • Management and ease of use - Consider the ease of deployment, configuration, and ongoing management. Is it easy to deploy and manage? Is it a separate product, with a separate console, that requires full-time specialists to maintain, operate, and troubleshoot? 
  • Licensing and cost - Understand the licensing model and associated costs. Consider factors such as upfront expenses, ongoing maintenance fees, and any additional charges for advanced features.
  • 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, Microsoft Exchange, SAP, Oracle, Citrix, Splunk, and VMware Horizon?
  • Hypervisor Type (Type 1 or Type 2) - Determine whether a Type 1 or Type 2 hypervisor is more suitable for the organisation's specific use case, considering factors like performance, security, and deployment scenarios.
  • Virtualisation management tools - Consider the availability and functionality of virtualisation management tools provided by the hypervisor, such as monitoring, reporting, and automation features.

Benefits of Nutanix hyperconverged infrastructure solutions

The benefits of moving from complex legacy infrastructure to the simplicity of hyperconvergence are many, but among the top reasons organisations make the switch are lower costs, improved, consistent performance, a smaller datacentre footprint, greater efficiency and productivity in IT teams, and maximised infrastructure ROI.

  • Turnkey infrastructure - Integrated server, storage, networking and virtualisation resources along with comprehensive systems management and operations management capabilities.
  • Fast deployment - Deploy infrastructure in minutes, allowing IT teams to shift their focus to the applications and services that drive the business.
  • 100% software-driven - Supports a diverse range of hardware platforms, including three of the four most widely used server platforms globally.
  • Freedom of choice - Use built-in virtualisation or bring your preferred hypervisor, and deploy on a broad array of server vendors, or alternatively, buy a pre-integrated appliance from an original equipment manufacturer (OEM).
  • Superior performance and resilience - Nutanix HCI software running on each node distributes all operating functions across the cluster.
  • Unprecedented flexibility - A single cluster can have unlimited nodes, each with varying storage, CPU, and memory resources. This allows for running multiple workloads with maximum efficiency.

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