Understand the limitations of running Hyper-V in Windows 11

Why use Hyper-V in Windows 11?

The value of virtualization is clear for large and powerful enterprise servers, but the value proposition for endpoint systems can be more challenging to understand. Windows 11 is primarily intended for endpoint systems, such as desktop and laptop computers, where processors, memory and storage resources are far more limited than enterprise servers.

Virtualization does not create new resources -- it abstracts existing physical resources into logical equivalents which admins can provision and manage as independent virtual instances. Every new VM still consumes a portion of the local computer's available resources. Additional computing overhead is also imposed to handle the constant translation between physical and logical resources on the computer.

From a practical standpoint, the combination of limited computing resources and additional computing overhead will restrict most endpoint systems to just a few VMs -- rarely more than two or three. When an administrator deploys virtualization on Windows 11, it's typically to reduce the user's computer hardware needs.

Cross-compatibility

A typical endpoint computer installs a single OS and can only run software applications supported by that OS. When a user needs to run software that the local OS can't support, they need to install a different OS or use a different computer with the necessary OS. Neither option is particularly desirable. However, installing Hyper-V and creating a VM allows the user to create another logical computer on their existing system, and install a suitable OS such as Linux -- which does not affect Windows 11 running on the host computer. Then, they can install and run the desired application in that VM, all on the same physical computer.

Testing and development

Software developers routinely use desktop systems to code, build and test software. It's important to isolate the new build from the underlying system to ensure that any dependencies -- such as drivers and DLL files -- do not affect the host system. Developers will typically create a VM to serve as a blank system, allowing them to construct a suitable operating environment -- along with a preferred OS, drivers and other dependencies -- for bug testing, stress testing and other evaluations of the new build. In this case, the virtualization provides a quick and convenient means of creating a new, isolated and independent virtual computer without the need to buy actual hardware.

Requirements and limitations of Hyper-V on Windows 11

Hyper-V on Windows 11 -- sometimes referred to as client Hyper-V -- is part of the Windows 11 Pro and Enterprise OS, though it is generally not enabled by default. One of the first requirements is to enable the Hyper-V role in the Windows OS itself. To enable the Hyper-V role through Settings on Windows 11, for example, follow these steps:

• Open the Control Panel.
• Select Programs, then Programs and Features.
• Select Turn Windows Features on or off.
• Select Hyper-V and then select OK.

The computer should restart once the Hyper-V installation is completed.

A second significant requirement is to only deploy Hyper-V on computers with processors capable of second-level address translation (SLAT). Almost all modern endpoint processors carry this capability that is essential for performing the fast physical-to-logical resource translations necessary for efficient virtualization performance.

In addition, processors must include support for the VM Monitor Mode command set extensions -- this is known as VT-c on Intel processors. A minimum of 4 GB RAM is highly recommended. Fortunately, most modern PCs can provide well over 16 GB of RAM.

Once the installation is successful, users can create and manage VMs within Windows 11. However, there are several limitations to the client Hyper-V version which Windows 11 administrators should keep in mind:

• No VM clustering or replication, which is available with Hyper-V on Windows Server versions.
• No VM migration, though users can export and import VMs.
• No support for single-root I/O virtualization, which would allow devices to separate access to resources among different PCIe hardware functions.
• No virtual Fibre Channel support, though client Hyper-V can still use FC-attached storage.
• No RemoteFX, which supports remote display performance for uses such as VDI.

These features are primarily intended for enterprise-class VMs on Windows Server platforms. Restricting these features for Windows 11 will typically not impair VM usage in common endpoint, single-point use cases such as software testing.

Computer performance is also limited by factors such as clock speeds, bus architectures, chipset selection and other design attributes.

Practical limitations of Hyper-V on Windows 11

Virtualization is an important tool for modern computing, and Hyper-V is a reliable and well-proven offering for both servers and endpoints. But there are some practical limitations for endpoint users to consider when installing and using Hyper-V on Windows 11, including the following:

• Memory limitations. Plan on about 4 GB per VM. That might sound like a lot of memory, but it's important to remember that each VM will require its own OS, application workloads and other dependencies such as drivers and agents. The 4 GB goes fast. Most modern endpoint computers have 16-32 GB of RAM, so it's rarely a direct constraint, but it's important to understand that an endpoint system probably has enough memory for just a few VMs.
• Processor limitations. A VM typically requires a minimum of one CPU core per VM. While high-end processors can support 12-14 cores, more modest endpoint systems can still include processors with four-eight cores. This also limits the number of VMs that the system can support. Remember that the host running Hyper-V in the first place needs sufficient processing.
• System performance limitations. Computer performance is also limited by factors such as clock speeds, bus architectures, chipset selection and other design attributes. Even when a processor has numerous cores and plenty of memory, the data exchanged between the processor and memory storage, or I/O -- such as a display -- all has to traverse a single bus. The same connections cannot service all VMs at the same time and must be time-shared. The more VMs present on the system, the more that system architecture and performance limitations will affect VM performance. It's difficult to know precisely how much this impact might be, but it's still worth considering.
• Hardware dependencies. Software written with specific hardware dependencies might not perform well within a VM. For example, some games or math-intensive software might have trouble interacting smoothly with the system's GPU. Older legacy applications written to access specific hardware directly -- such as a particular CPU model -- can also experience serious problems within a VM. Fortunately, these applications can still be run on the host. In addition, programs that are latency-sensitive or demand high-precision timing -- such as audio or video editing apps -- can be problematic within a VM.

Overcoming the limitations of Hyper-V on Windows 11

The limitations of client Hyper-V on Windows 11 endpoints can be difficult to overcome and are typically not cost-effective or outcome-efficient enough simply to run a few VMs on an everyday endpoint. However, there are still some strategies that can help with these smaller scale use cases:

• Install Windows 11 updates regularly. Be sure to keep Windows 11 up to date, especially updates that involve virtualization components such as the core hypervisor software and virtualization drivers.
• Update system BIOS. BIOS -- or firmware -- is the fixed code that boots the system and provides the foundational code needed for hardware devices to interoperate. Any firmware updates intended to improve virtualization services for the CPU, such as SLAT, are essential. Also look out for updates that enhance chipset or bus management to improve virtualization -- though the improvements are typically small.
• Update drivers for hardware dependencies. When software within a VM must communicate with hardware devices such as GPUs or network functions, updating the corresponding drivers within the VM can improve performance. Check the driver release notes for specific stability and performance enhancements intended for Hyper-V.
• Consider using Windows Server. When endpoint users must run numerous VMs with vital capabilities that client Hyper-V lacks, such as clustering or replication as noted previously, it might be worth considering a change. Dedicating a capable endpoint system to a version of Windows Server 2022 or later rather than Windows 11 could provide better overall performance. However, this can be a costly option for individuals and small businesses.
• Try a different virtualization platform. Client Hyper-V is just one virtualization platform. VMware's ESXi and open source Xen are just two alternatives to consider. Adopting these tools will require extensive time and testing to ensure they provide the services, performance and support required.

Stephen J. Bigelow, senior technology editor at TechTarget, has more than 30 years of technical writing experience in the PC and technology industry.