Type 2 virtual machines (VMs) are virtual machines where the hypervisor runs on top of a host operating system, rather than interacting directly with the hardware. The hypervisor relies on the underlying OS for resource management and access. This means type 2 hypervisors have some advantages and disadvantages compared to type 1 hypervisors.
Advantages of Type 2 VMs
Some of the key advantages of using type 2 VMs include:
- Easier to install and configure: Type 2 hypervisors can be installed as an application on an existing OS, which allows for easier installation and configuration. Administrators don’t need to install a bare-metal OS.
- Better portability: The type 2 hypervisor and virtual machine images can be easily ported across different OS platforms running on the hardware. For example a type 2 hypervisor on Windows can be ported to run on Linux or macOS.
- Makes use of host OS drivers: This allows the type 2 hypervisor to make use of drivers and features in the host OS like power management, graphics and networking protocol stacks. This can improve performance and compatibility.
- Snapshots and Live Migration: The hypervisor can leverage the host OS file systems to efficiently manage VM snapshots. Migrations of live VMs from one host system to another is also easier.
- Cost Savings: No need for dedicated server hardware to install an OS directly on the hardware. A type 2 hypervisor allows VMs to run on lower cost normal PCs and laptops running host OSes.
Disadvantages of Type 2 VMs
Some of the disadvantages include:
- Performance Overhead: The hypervisor and guest VM all compete for the underlying hardware resources through the host OS, which causes performance degradation compared to type 1 VMs.
- Less Security: Vulnerabilities in the host OS may allow guest VMs to be compromised for malicious purposes.
- Host Reboot Impact: If the host OS needs rebooting, all the dependent guest VMs are impacted. A type 1 hypervisor runs separately so host reboots don’t affect VMs.
Common Type 2 Hypervisors and Virtualization Platforms
Some of the most common enterprise grade type 2 hypervisors and virtualization platforms include:
- VMware Workstation/Fusion
- Oracle VirtualBox
- Parallels Desktop
- Microsoft Hyper-V
- Citrix XenClient
On the desktop side, VMware Workstation and Oracle VirtualBox are very popular to allow running multiple guest OSes on a single host system.
For large server infrastructure deployments, VMware vSphere which runs on vCenter Server features a type 2 hypervisor architecture. The VMware ESXi hypervisor integrates very closely with vCenter for full lifecycle management.
Here is a high level architectural comparison between running VMs on ESXi type 1 hypervisor vs Workstation’s type 2 hypervisor:
The type 1 ESXi hypervisor runs directly on server hardware without a host OS while Workstation runs as an application on a host OS.
Workstation type 2 VMs rely on the host OS to provide I/O device drivers and machine resources to guest VMs. ESXi interacts directly with hardware for I/O and CPU/memory resources, running VMs bare metal.
So in summary, while the end experience of managing VMs seems similar from admin and user perspectives, under the hood there are significant architectural differences between type 1 and type 2 virtualization platforms.
When To Use Type 2 vs Type 1 Hypervisors?
Here are some guidelines on when to choose between type 2 and type 1 hypervisors:
Type 2 Recommended When:
- You need to run VMs on desktops, laptops and other PCs
- Seeking ease of installation on existing OS platforms
- Don’t need maximum VM density and performance
- Useful for development, test, QA systems before full scale deployment
Type 1 Recommended For:
- Running production environments at cloud scale
- Requires maximum performance, scalability and security
- Sensitive, mission critical workloads & data
- Hyperconverged infrastructure solutions
- Software defined datacenter deployments
So in summary type 2 works well for desktop usages while type 1 fits enterprise scale cloud infrastructure needs.
Type 2 hypervisors run guest VMs by relying and building on top of host operating systems. This provides advantages like easy installation and portability across different platforms. But the tradeoff is there can be reduced performance, density and security compared to type 1 bare-metal hypervisors.
Leading type 2 virtualization software solutions include VMware Workstation, Oracle VirtualBox and Microsoft Hyper-V. These are popular for desktop usage scenarios for running VMs.
Type 1 hypervisors that run directly on server hardware are better suited for large scale production deployments that demand the highest VM performance. Solutions like VMware ESXi and vCenter Server, Microsoft Hyper-V and Red Hat Virtualization excel in the data center.
- Type 2 hypervisors run as software on host OS providing portability but reduced performance vs type 1.
- Best suited for desktop usage, development/test environments before production deployments.
- Leading solutions include VMware Workstation, VirtualBox, Hyper-V and Parallels Desktop.
- Type 1 runs directly on hardware ideal for cloud scale mission critical workloads.
Frequently Asked Questions
- What’s the difference between type 1 and type 2 hypervisors?
A: The key difference is type 1 runs directly on server hardware while type 2 runs as a software layer on an existing host operating system. Type 1 offers higher performance while type 2 trades off some performance for easier installation and portability.
- What is an example of a type 2 hypervisor?
A: Some examples include VMware Workstation/Fusion, Oracle VirtualBox, Microsoft Hyper-V Client, and Parallels Desktop. These run as an application on host OSes like Windows, Linux or macOS.
- Why is a type 2 hypervisor considered less secure than type 1?
A: Since type 2 relies on a host OS, any vulnerabilities in the host OS could allow guest VMs to be compromised. Type 1 runs directly on hardware isolated from any host OS providing stronger security.
- Can you run a type 2 hypervisor on an enterprise server?
A: While possible, for performance reasons it is recommended to run type 2 hypervisors for desktop usage and utilize type 1 for production datacenter usage. Type 1 can provide the necessary density, performance and reliability needed.
- Is VMware Workstation an example of a type 2 hypervisor?
A: Yes, VMware Workstation which runs on Windows and Linux hosts is a very popular type 2 hypervisor allow running multiple guest OSes as VMs on a single host desktop or laptop system.
- Does Hyper-V use a type 1 or type 2 hypervisor architecture?
A: Microsoft Hyper-V comes in two forms – a native type 1 hypervisor that runs directly on hardware called Hyper-V Server. And the client Hyper-V on Windows uses a type 2 hypervisor architecture and runs as an application.
- Can you live migrate VMs on a type 2 hypervisor?
A: Type 2 hypervisors that integrate with backend OS platforms can allow live migration of VMs from one host system to another similar host seamlessly allowing zero downtime.
- Will type 2 hypervisors replace or obsolete type 1 hypervisors in the future?
A: No, type 1 and type 2 hypervisors address very different usage scenarios. Type 2 works for desktop use cases while type 1 excels for enterprise scale cloud infrastructure so both will continue to be relevant.
- Is a type 2 hypervisor more difficult to install than type 1?
A: Typically type 2 hypervisors are far easier to install as they can be rapidly deployed like any other software application on existing host operating systems. Type 1 requires bare metal installation.
- If a host OS crashes, what happens to VMs running on a type 2 hypervisor?
A: The guest VMs and type 2 hypervisor rely entirely on the host operating system. So if the host OS crashes, all the dependent guest VMs will crash and be unavailable until the host OS reboots and recovers.
- Can you use Docker containers with a type 2 hypervisor?
A: Yes, type 2 hypervisors like Workstation and VirtualBox running on Linux hosts allow you run Docker containers inside of guest VMs. This allows combining the isolation of VMs and containers.
- What are some best practices for running type 2 hypervisor VMs?
A: Some best practices include staying up-to-date on hypervisor and host OS security patches, properly allocating vCPU cores, memory and storage to prevent host resource starvation, isolating VM and host networks, and replicating VMs to allow fast disaster recovery.
- What platforms support deploying the Oracle VirtualBox type 2 hypervisor?
A: Oracle VirtualBox can run on a wide range of host operating systems including Windows, Linux, macOS, Solaris and Open Solaris. This allows VirtualBox to support easy portability across many client and server platforms.
- Is it better practice to shut down or suspend VMs running on a type 2 hypervisor?
A: Shutting down cleanly stops all processes allowing the hypervisor to sync VM states. Suspend can quickly save state but takes up host resources. Shut down when VMs won’t be used for a while and suspend/resume to quickly pause and start VMs.
- Can you convert a VM from a type 2 hypervisor to then run on a type 1 hypervisor?
A: Yes, through standard virtual machine image conversion tools like VMware vCenter, it is possible to convert a VM originally created on say VMware Workstation to then run on the ESXi type 1 hypervisor.
- Which is cheaper – hardware supporting type 1 or type 2 hypervisor deployments?
A: Type 2 hypervisors allow you to repurpose existing standard desktops, servers and laptops as VM hosts which saves on hardware costs. Specialized hardware is recommended for large type 1 deployments instead to provide the required performance levels.
- Can type 2 hypervisors utilize GPUs?
A: Yes – type 2 hypervisors like Workstation and VirtualBox now support GPU passthrough to allow VM guest machines direct access to the high performance graphics capabilities.
- Do you have to reboot type 2 hypervisor host machines after upgrading?
A: After upgrading the type 2 hypervisor software itself, typically rebooting the host OS is not necessary. But some underlying host kernel security updates may require rebooting to apply patches.
- What backup solutions exist for type 2 hypervisor VMs?
A: Solutions like Veeam Backup support backing up changes block-level changes to VM disk files daily to allow restoring individual files or entire VMs. Site replication of VM files is recommended to protect against host hardware failures.
- Can I load an existing physical server OS directly into a type 2 hypervisor VM?
A: Yes – type 2 hypervisors like VMware Workstation allow directly applying a P2V (Physical to Virtual) process to convert a physical machine into a reusable VM image which loads the original OS. This allows migrating physical servers into VMs.