When Microsoft created Windows Server 2016, it provided the ability to deploy the OS as a Nano Server. Nano Servers...
have a far smaller footprint than server core deployments and are intended for headless operations. Although Nano Server is somewhat limited in its capabilities, a Nano Server can act as a Hyper-V host. As such, it's worth considering whether it's better to run Hyper-V on top of Nano Server or to use a more traditional OS deployment type.
The first thing to consider when deciding whether or not to run Hyper-V on Nano Server is whether doing so means giving anything up. Although Nano Server is somewhat limited in what it can be used for, Nano Servers can be used as Hyper-V hosts, and can also be domain joined and configured as nodes within a failover cluster. From a functionality standpoint, Hyper-V behaves in the same way regardless of whether it's running on Nano Server, server core or a full GUI-based deployment of Windows Server. Even so, there are significant differences when it comes to deploying and managing Hyper-V.
Challenges of using Nano Servers as Hyper-V hosts
If you've performed a Windows Server 2016 deployment, then you've probably noticed that there isn't an option within the installation wizard to deploy Windows as a Nano Server. For whatever reason, Microsoft requires its customers to build Nano Server deployment images, and then use those images to deploy Nano Server. Until recently, deploying and configuring Nano Server was a manual process. Today, admins have the option of either using the manual deployment process or using the Nano Server Image Builder, a graphical tool for creating Nano Server images.
Regardless of how an administrator opts to deploy Nano Server, Nano Server's footprint is tiny. Typically, a Nano Server image is at least 20 times smaller than a Windows Server image that includes the desktop experience. One of the ways that Microsoft was able to make Nano Server so small was by getting rid of the administrative interface. Nano Servers have a small, text-based console that can be used to set the server's IP address and configure its firewall, but most other management tasks must be performed remotely. In the case of Hyper-V, this means that administrators will have to run either the Hyper-V Manager or the Virtual Machine Manager console on another computer and manage Nano Server remotely.
For Hyper-V administrators, there tends to be a significant learning curve associated with the initial deployment and configuration of Nano Server. Once the initial setup is complete, however, managing Hyper-V should feel completely familiar for anyone who has prior Hyper-V experience. Even so, Hyper-V administrators will need to consider whether third-party software will work with Nano Server. Some examples of such software may include virtualization management and reporting software, antimalware software and backup agents.
Advantages of running Hyper-V on Nano Servers
Although working with Nano Server can take a bit of getting used to, there are some significant benefits to running Hyper-V on top of Nano Server. For starters, Nano Server consumes fewer system resources than other types of Windows Server deployments. This means that some of the resources that would have otherwise been used to run the server's OS can instead be used for hosting VMs.
Nano Server can also significantly ease the patch management burden for virtualization hosts. Hyper-V has long supported rolling patch management for clustered Hyper-V deployments. This process live migrates the VMs off, patches and reboots the node, and then repeats the process for the next node in the cluster until all of the nodes have been upgraded. Although this technique allows for patches to be applied without causing VMs to be taken offline, the patch management process can impact performance while patches are being applied.
The same basic technique is used for patching clustered Hyper-V deployments that are based on Nano Servers, but Nano Server's small footprint means that it should require far fewer patches than other types of Windows Server deployments. This also means that Nano Server will have to be rebooted less frequently than other Windows Server deployment types, which means there will be a reduced need to live migrate VMs, thereby reducing the performance impact of the patch management process. While it's true that reboots can't completely be avoided, Nano Server's small size allows the OS to boot in a matter of seconds.
Deploying and configuring Nano Server can be extremely challenging. Even so, Hyper-V is managed in the same way on Nano Servers as on other server deployment types. Although Nano Server might not be the best choice for every situation, in most cases running Hyper-V on Nano Server will yield significant performance and patch management benefits.
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