A hypervisor is software that creates and runs virtual machines (VMs). It’s also known as a virtual machine monitor (VMM). It allows one physical machine to run multiple VMs each with its own operating system and set of applications.
This guide will help you understand what a hypervisor does, how it works, and why it’s essential for modern IT environments.
Hypervisor Definition
A hypervisor is a software layer that sits between hardware and operating systems. It manages system resources and allocates them to multiple operating systems running on the same physical machine.
In simple terms, it lets you run many computers inside a single computer. It’s the technology that makes virtualization possible.
How a Hypervisor Works
When you boot a traditional computer, the hardware runs one operating system (OS). A hypervisor changes that. It introduces a layer between the hardware and any OS that wants to run on the system. This layer creates and manages VMs, each behaving like a separate computer.
Hypervisors use various components commonly found in operating systems, such as memory management, process scheduling, input/output handling, device drivers, security features, and networking functions, to run VMs.
They assign the necessary resources to each VM and coordinate how these virtual resources interact with the physical hardware. The physical machine still performs the actual tasks. For example, the CPU executes instructions from the VMs while the hypervisor manages the scheduling.
Virtualization allows multiple operating systems to run at the same time on a single set of hardware. Without virtualization, only one operating system could run on the hardware.
What Does a Hypervisor Do?
A hypervisor assigns CPU, memory, storage, and other resources to each VM based on demand, making sure the host server operates efficiently. A hypervisor also keeps VMs separate from one another, so activity in one VM doesn’t affect the others.
By enabling multiple VMs to run on a single physical machine, it makes better use of hardware and lowers infrastructure costs. In addition, the hypervisor serves as a bridge between the virtual machines and the underlying hardware, translating VM instructions into commands the physical system can execute.
Types of Hypervisors
There are two main types of hypervisors: Type 1 and Type 2.
Type 1 Hypervisor
A Type 1 hypervisor runs directly on the physical hardware. It’s also known as a bare metal hypervisor. It does not need a host operating system. This makes it faster and more efficient because it communicates directly with the system’s resources.
Examples of Type 1 Hypervisors:
- VMware vSphere (ESXi)
- Microsoft Hyper-V
- KVM (Kernel-based Virtual Machine)
Use Cases and Benefits
Type 1 hypervisors dominate enterprise virtualization. They run directly on hardware, enabling powerful, scalable, and secure environments for critical workloads.
- High Performance: Bare metal hypervisors deliver top efficiency by interacting directly with CPUs, storage, and memory. Modern processors with built-in virtualization features boost this even further.
- Enterprise-grade Reliability: IT teams run production workloads on type 1 hypervisors to ensure high uptime, failover support, and stability.
- Scalability: These hypervisors are scalable and handle large volumes of data, making them ideal for big, complex environments.
- Advanced Capabilities: Most type 1 hypervisors support software-defined networking and storage.
- Built for the Cloud: Type 1 hypervisors are a popular choice to power private and public cloud infrastructure.
Type 2 Hypervisor
A Type 2 hypervisor runs on top of a host operating system like Windows, Linux, or macOS. It is essentially an application that provides virtualization capabilities.
Examples of Type 2 hypervisors:
- VMware Workstation Pro
- Oracle VirtualBox
- Parallels Desktop
Use Cases and Benefits
Developers or IT managers can use type 2 hypervisors for their speed and flexibility.
- Easy and Fast to Set Up and Use: Type 2 hypervisors are installed as regular applications, requiring no complex configuration. It is ideal for lightweight workloads.
- Testing and Developer-friendly: Engineers use them to run multiple OS environments for app testing.
- Educational: Professors suggest type 2 hypervisors to students for studying different operating systems and network settings without a negative impact on students’ host machines.
Type 1 vs Type 2 Hypervisors: A Side-by-Side Comparison
| Feature | Type 1 Hypervisors | Type 2 Hypervisors |
| Runs On | Physical hardware directly | Host operating system |
| Performance | Efficient | Lower due to host OS overhead |
| Security | Stronger (smaller attack surface) | Weaker (relies on host OS) |
| Setup Complexity | Higher | Simple, user-friendly |
| HCI Integration | Commonly used | Rarely used |
| Examples | VMware ESXi, Microsoft Hyper-V, KVM | Oracle VirtualBox, VMware Workstation Pro, Parallels Desktop |
The Hypervisor Market
The hypervisor market is dominated by discussion of Broadcom’s changes to the VMware vSphere product licensing. This includes changes like moving licensing to subscriptions and developing a 3-year commitment to renewals. This requires users of vSphere to commit in advance for a three-year period, essentially ‘locking in’ costs and requiring an upfront payment. Previously, many customers renewed annually, providing more flexibility.
These changes have led to many hypervisor users weighing up the benefits and challenges of VMware migration. While leading research bodies, such as Gartner, cite that doing so could be long, expensive, and risky.
However, since Broadcom announced these changes in 2023, many vendors have had time to develop and promote new solutions that offer a competitive alternative to VMware products.
In today’s market, these vendors have evolved quickly, demonstrating that they can deliver purpose-built, dependable, and cost-effective solutions. They offer low-risk and lower total cost of ownership alternatives, which are driving change in the market.
6 Key Benefits of Hypervisors
1. Server Consolidation
Instead of running one application per physical server, hypervisors allow multiple workloads to share the same hardware. This consolidation significantly reduces the need for additional hardware, lowering capital and operational costs related to power, cooling, and physical space. It also simplifies the IT environment, making it easier to manage, update, and scale infrastructure.
2. Improved Resource Utilization
A hypervisor dynamically allocates CPU, memory, and storage to virtual machines based on their needs. This ensures that no hardware sits idle while other parts of the system are overburdened. As a result, organizations achieve higher efficiency and performance without needing to invest in additional hardware.
3. Easy Backup and Recovery
Virtual machines can be cloned, backed up, and restored quickly. In the event of a failure, they can restore a VM to a previous state with minimal downtime. This enhances disaster recovery strategies and ensures business continuity by reducing the time needed to recover from hardware failures or software issues.
4. Better Testing and Development
Developers use hypervisors to test software on multiple platforms without needing separate hardware. Developers can run multiple operating systems on a single machine, test compatibility across platforms, and use VM snapshots to save the current state of a VM. If something breaks during testing, they can quickly revert to the saved state, speeding up the development cycle and reducing the risk of errors.
5. Greater Security and Isolation
Each virtual machine operates in its own isolated environment. If one VM is compromised, it does not affect others. This level of isolation is critical in environments where multiple users or departments share the same hardware. It also, in some cases, can help organizations enforce security policies and minimize the spread of malware or vulnerabilities across systems. However, hypervisors should always be used in environments that have more extensive and comprehensive security and backup policies in place.
6. Portability
In the context of data, “portable” refers to the ability to easily move and reuse data. The VMs that the hypervisor runs are independent from the physical machine, making them portable. IT teams can manage workloads, networking, memory, storage, and processing resources across multiple servers as needed. Crucially, if more applications are required, it’s straightforward to add additional VMs.
Hypervisor vs Containers
While hypervisors and containers both support virtualization, they work differently. Although at a top level they seem similar, as they both package computing environments, they are different in how they scale and their portability.
- Hypervisors virtualize hardware. Each VM runs a full operating system.
- Containers virtualize the operating system. They share the same OS kernel but isolate applications in separate environments.
Hypervisors offer strong isolation and are ideal for running multiple OS types. Containers are lightweight and work well for microservices and DevOps pipelines.
While a hypervisor makes it possible to run several operating systems across different VMs, containers are tied to a single operating system type. For instance, a container hosted on a Linux system can only run Linux-based workloads.
Although some view containers as a replacement for hypervisors, that’s not entirely accurate. Each serves distinct purposes and addresses different technological requirements.
Hypervisor FAQs
What’s the Best Hypervisor for a Homelab?
A homelab is a self-contained IT environment that you design and control. As the IT landscape continues to shift toward decentralization and hybrid infrastructure, the need for hands-on learning has never been greater. Homelabs offer a flexible, low-risk way to explore technologies.
Hyperconverged infrastructure (HCI) software, such as SvHCI, is designed for environments with limited space and power, which makes it a natural choice for homelabs. It enables you to test features and focus on learning functionality, making it an ideal hypervisor choice for a homelab.
What is the Function of a Hypervisor?
Hypervisors help use a system’s resources more efficiently and increase flexibility because guest VMs don’t rely on specific hardware. You can move them easily from one server to another. Since a hypervisor lets multiple VMs run on a single physical server, it also helps reduce the physical space needed, energy use, and maintenance work.
What are the Key Hypervisor Security Considerations?
A VM runs in its own isolated environment, so anything inside the VM stays separate from the rest of the system. This isolation means that whatever runs in one VM won’t affect other programs or processes on the physical machine.
If someone hacks into a VM, that attack usually stays within that VM and doesn’t spread to the rest of the system. But if an attacker manages to break into the hypervisor, they could access every VM it manages. That would put all the data in those VMs at risk.
Different hypervisors may follow different security rules or need different protections, depending on how they’re built and used.
