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Clearing up the Nano Server vs. Server Core confusion

The debut of Windows Server 2016 contained a lighter server OS deployment to replace Server Core, but then Microsoft made a drastic change that still has some admins puzzled.

Microsoft has two Windows Server deployment options with a smaller code base than the GUI version. When comparing Nano Server vs. Server Core, do you know the difference?

Microsoft calls the full deployment of its server operating system the Server with Desktop Experience. As the name indicates, this installation provides the traditional Windows layout with menus accessed via a mouse or keyboard, similar to a standard Windows 10 system. Many administrators prefer the GUI deployment for the familiar desktop layout, which makes it easier to manage in some instances. In some cases, this full server OS deployment is the only option to run certain applications. For example, System Center Server Virtual Machine Manager 2019 and SharePoint Server 2019 both rely on the Server with Desktop Experience to function.

To fully understand a Nano Server vs. Server Core comparison, some context is needed. To do this, it helps to know the history behind these reduced Windows Server deployments to see how they started and then evolved along the way.

Server Core

Microsoft debuted the Server Core deployment with Windows Server 2008. As a headless deployment option, Server Core has no GUI and must be managed with PowerShell or command-line utilities or remote user interface tools, such as Windows Admin Center or Remote Server Administration Tools.

Server Core can be used as a host for containers or Hyper-V VMs or to run infrastructure workloads, including file servers, domain controllers and domain name servers. While Microsoft recommends Server Core as the default deployment option, it only recently began to support the use of Exchange Server on Server Core.

Microsoft said the tradeoff for an OS that requires more technical skill to administer is a smaller attack surface that should -- at least, in theory -- require fewer patches and, therefore, less downtime due to the need to reboot after patching.

Nano Server

Microsoft added a new server deployment option in Windows Server 2016 called Nano Server. The company promoted Nano Server as a successor to Server Core, as a smaller, even more secure headless deployment. Microsoft said Nano Server was optimal for many of the same infrastructure workloads handled by Server Core, such as an IIS web server or as a host for containers or Hyper-V VMs.

But there continues to be some confusion for administrators who wonder whether to use Nano Server vs. Server Core for infrastructure workloads, because Nano Server got a complete overhaul several months after the release of Windows Server 2016. Microsoft decided to make some significant changes to the product approximately eight months after launching Windows Server 2016.

Changes to Nano Server

Microsoft released Windows Server 2016 in September 2016. In June of the following year, the company released a blog indicating Nano Server would lose its infrastructure capabilities and any Microsoft support for these workloads. The company said it would strip down the Nano Server code base even further to repurpose it strictly for use with containers.

In a blog entitled "Delivering continuous innovation with Windows Server," Microsoft said the feature change in Nano Server came about after customers requested an OS build more tailored for containers.

"Based on that feedback, we are making an important change to Nano Server. This next release will focus on making Nano Server the very best container image possible. From these changes, customers will now see the Nano Server images shrink in size by more than 50 percent, further decreasing startup times and improving container density. As part of this effort to focus on containers, we will be removing the functionality for infrastructure-related roles. Instead of using Nano Server for these scenarios, we recommend deploying the Server Core installation option, which includes all the roles and features you would need," Microsoft wrote in the blog.

New servicing options bring additional changes

In the same blog that revealed the refined purpose for Nano Server, Microsoft also shared plans for a new servicing channel program for Windows Server that would consist of two channels rather than one.

The Long-Term Servicing Channel (LTSC) -- previously known as the Long-Term Servicing Branch -- is the channel for the long-standing servicing option with five years of mainstream support, followed by five years of extended support. Feature updates for Windows Server in the LTSC would continue to follow the customary two or three years between releases.

The Semi-Annual Channel for Windows Server would follow the release and support cadence of the Windows 10 SAC: a major release every six months with 18 months of mainstream support and no option for extended support. Microsoft said SAC is meant for enterprises that follow the quicker pace of DevOps that want the newest features and updated functionality as quickly as possible.

Microsoft said Nano Server and Server Core would be part of the SAC, while Server Core and Server with Desktop Experience would belong to the LTSC. Despite Server Core appearing to belong to both channels, the SAC and LTSC Server Cores are not interchangeable due to the difference in support terms.

To run containers on Windows, Microsoft offers several base images used to build the container image. Each base image offers different functionality depending on the type of container workload to run. The container base images are Nano Server, Windows, Server Core or Windows 10 IoT Core.

Customers who do a search for Nano Server on Microsoft's site will still find outdated documentation for Windows Server 2016 that details the original purpose of this deployment option.

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