What is a Hypervisor?
A hypervisor — also called a Virtual Machine Monitor (VMM) — is the software layer responsible for managing the physical hardware resources of a server, including CPU, memory, storage and network bandwidth. It divides these resources into isolated virtual machines (VMs), each running its own operating system and applications independently of the others.
A hypervisor lets one physical server behave like many separate computers. Each virtual machine thinks it has its own dedicated hardware — but in reality, the hypervisor is sharing the physical resources between all of them efficiently and securely.
Type 1 vs Type 2 Hypervisors
There are two categories of hypervisor, each suited to different environments and use cases.
Runs directly on hardware
- No underlying operating system required
- Direct access to physical hardware resources
- Higher performance and lower latency
- More secure — no host OS attack surface
- Used in enterprise data centres
- Examples: VMware ESXi, Microsoft Hyper-V, Nutanix AHV, eEVOS
Runs on top of an OS
- Installed on an existing operating system
- Relies on the host OS for hardware access
- Lower performance than Type 1
- Easier to install and use
- Used for development and testing
- Examples: VMware Workstation, Oracle VirtualBox
For enterprise data centre deployments, Type 1 bare-metal hypervisors are the standard. They offer better performance, stronger security, and more reliable isolation between virtual machines. Type 2 hypervisors are typically used by developers running test environments on their own workstations.
How a Hypervisor Works
When a hypervisor runs on a server, it creates a virtualisation layer between the physical hardware and the operating systems running above it. Each virtual machine receives a defined allocation of CPU cores, RAM, storage, and network bandwidth. From the VM's perspective, it appears to have dedicated hardware — it has no awareness of the other VMs running on the same physical machine.
The hypervisor manages all requests from virtual machines to access physical hardware, scheduling them efficiently and ensuring one VM cannot access another's memory or storage. If a guest operating system crashes, only that VM is affected — the hypervisor and all other VMs continue running normally.
Configuring a Virtual Machine
Setting up a virtual machine on a hypervisor is straightforward. The process typically involves selecting the guest operating system, allocating CPU, memory and storage resources, configuring the network, and setting login credentials. The VM then runs as a fully independent system within the hypervisor environment.
Modern hypervisors provide centralised management tools that allow administrators to monitor all VMs, apply updates, take snapshots, clone machines, and migrate workloads between physical hosts — often without any downtime for the running applications.
Hypervisors and Storage
Storage is a critical component of any virtualised environment. Each VM needs access to fast, reliable storage — and as the number of VMs increases, so does the I/O demand on the underlying storage infrastructure. This is why hypervisor environments typically require purpose-built enterprise storage rather than generic server-attached storage.
All-flash NVMe storage dramatically improves the performance of virtualised workloads — reducing latency and increasing the number of VMs a physical host can support efficiently. Hypervisors also support storage-level features including snapshots, replication, and thin provisioning that complement the VM management capabilities of the hypervisor itself.
Need to design a storage architecture for your virtualised environment? Our specialists can recommend the right solution for your workload.
Speak to a storage specialist →Hypervisors and VDI
Virtual Desktop Infrastructure (VDI) is one of the most common enterprise use cases for hypervisors. Rather than running a desktop operating system locally on each user's machine, VDI delivers a virtual desktop from a centralised server over the network. The endpoint device — which can be a thin client, laptop, or tablet — simply displays the desktop session.
The benefits are significant: all data and processing remain on the server, simplifying security management. Endpoint devices can be low-cost thin clients with long lifespans since they do no local processing. Software updates are applied once on the server rather than across hundreds of individual machines. And users can access their desktop from any device.
Hypervisors and HCI
Hyperconverged Infrastructure (HCI) builds on the hypervisor concept by combining compute, storage, and networking into a single software-defined platform. Rather than separate storage arrays connected to separate servers, an HCI system like Nutanix runs the hypervisor directly on nodes that also provide distributed storage — managed as a unified cluster.
HCI simplifies deployment and management significantly, making it well suited to organisations that want the benefits of virtualisation without the complexity of designing and managing separate compute and storage tiers. The tradeoff is that scaling compute and storage together (rather than independently) can be less efficient for workloads with highly asymmetric requirements.
Key Hypervisor Features
Live migration
Move running VMs between physical hosts without downtime — essential for hardware maintenance and load balancing.
High availability
Automatically restart VMs on another host if a physical server fails. Protects against hardware failure with minimal manual intervention.
Snapshots
Point-in-time captures of a VM's state — used for backup, testing, and rapid rollback after failed updates.
Resource scheduling
Dynamically balance VM workloads across hosts to maximise utilisation and prevent performance bottlenecks.
Cloning
Rapidly deploy new VMs by cloning existing ones — dramatically reducing provisioning time for new workloads.
Replication
Replicate VMs to a secondary site for disaster recovery — either via the hypervisor or storage-level replication.
Frequently Asked Questions
What is a hypervisor in simple terms?
A hypervisor is software that allows one physical server to run multiple virtual machines at the same time. Each virtual machine operates independently with its own operating system and applications, while the hypervisor manages the underlying physical hardware and shares it between all the VMs.
What is the difference between Type 1 and Type 2 hypervisors?
A Type 1 (bare-metal) hypervisor runs directly on the physical hardware without an underlying operating system — it is faster, more secure, and used in enterprise data centres. A Type 2 (hosted) hypervisor runs on top of an existing operating system and is used mainly for development and testing on workstations.
What are examples of Type 1 hypervisors?
Common enterprise Type 1 hypervisors include VMware ESXi, Microsoft Hyper-V, Nutanix AHV, and eEVOS. All run directly on physical server hardware without a host operating system.
What is the difference between a hypervisor and a virtual machine?
The hypervisor is the software layer that creates and manages virtual machines. A virtual machine (VM) is the isolated computing environment that the hypervisor creates — it runs an operating system and applications as if it were a physical computer.
What storage do hypervisors need?
Hypervisor environments require fast, reliable enterprise storage that can handle the combined I/O of all running VMs. All-flash NVMe storage is increasingly the standard for virtualised workloads, delivering low latency and high IOPS that spinning disk cannot match at scale.
What is the difference between a hypervisor and HCI?
A hypervisor is the virtualisation software layer. HCI (Hyperconverged Infrastructure) is a complete infrastructure approach that combines the hypervisor, compute, and storage into a single software-defined platform — removing the need for separate storage arrays. Nutanix is the most widely known HCI platform.
