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The challenge Microsoft faces today is it must address two sets of customers. First, there are the application developers who work on continuous deployment cycles. And second, there are traditional IT pros who prefer consistency over speed.
To that end, Microsoft has moved Windows Server to a more formal release cycle it uses with its other products, such as Windows 10 and Office 365 ProPlus, which gives businesses a choice. A Long-Term Servicing Channel brings new releases twice a year to meet the needs of traditional enterprise deployments and a Semi-Annual Channel that serves cloud-centric organizations with short-term, fast-evolving environments that need fast access to new features.
Here are the services and features included in each Windows Server release schedule and what to expect for support and updates.
What are the new release channels for Windows Server?
Microsoft's long-held pattern is to introduce a major Windows Server release every two or three years, followed by roughly a decade of support. Microsoft calls this its Long-Term Servicing Channel, formerly known as the long-term servicing branch. Windows Server with Desktop Experience -- the full GUI-based installation -- and Windows Server Core iterations will follow the Long-Term Servicing Channel and get new rollouts every two or three years.
The more intriguing change is Microsoft's short-term release model, known as the Semi-Annual Channel. This approach promises a notable rollout each year in the spring and fall. This channel caters to organizations that want quick access to advanced capabilities, such as support for Linux Bash and the latest Docker container features. Volume-licensed businesses with the Software Assurance program are eligible for the Semi-Annual Channel release.
The Nano Server installation option now only exists in the Semi-Annual Channel. Server Core comes in both short- and long-term channel alternatives.
The Semi-Annual Channel lets Microsoft test and experiment with new server OS features and functionality, and then bundle the most successful and well-received enhancements into the long-term channel. There is no guarantee that all features placed in the Semi-Annual Channel will make it into the next long-term Windows Server release.
What are the support and update details for the channels?
Microsoft offers different support terms for the different release channels.
Long-Term Servicing Channel: These Windows Server products get five years of mainstream support, five years of extended support and an optional six more years of support through Microsoft's Premium Assurance program. This means Windows Server with Desktop Experience and the long-term version of Server Core receive up to 16 years of support.
That Long-Term Servicing Channel timeline applies to the Windows Server 2016 RTM, which rolled out in October 2016. It gets mainstream support until January 2022, with extended support until January 2027. With Premium Assurance, the support lifecycle for Windows Server 2016 finishes in 2033.
Semi-Annual Channel: Windows Server products in this release, such as Server Core and Nano Server, receive support for 18 months. Microsoft anticipates the shorter support window will be adequate, since new rollouts will arrive twice a year. This short-term channel is designed for organizations that want to change OSes quickly, such as cloud-ready data centers and IT infrastructures. Businesses that use the Semi-Annual Channel will likely update the OS long before the support expiration date.
Microsoft made the Windows Server Semi-Annual Channel fall release, known as Windows Server version 1709, available in October 2017. This means mainstream support ends in April 2019.
Security updates: Microsoft switched Windows Server's servicing model to a cumulative approach in October 2016. Admins used to choose to install or uninstall individual updates, but now there is a single monthly rollup with all the fixes. Each new monthly update -- released on the second Tuesday of each month, known as Patch Tuesday -- supersedes the previous updates.
This all-or-nothing approach ensures admins can't use a fragmented patching regimen. However, the IT staff must take a more thorough testing approach before the update rolls out to production.
As part of the Semi-Annual Channel release, Microsoft changed Nano Server to a container base image model in Windows Server version 1709. Because Nano Server has no servicing stack, the admin updates the OS through a deployment of the latest build of the runtime image via Docker.
Features in Windows Server version 1709
With the fall Semi-Annual Channel release of Windows Server, Microsoft focused on improving container features. The company repurposed the Nano Server installation option to a container-only image. Microsoft pulled Nano Server's infrastructure components and servicing stack to reduce the image from 390 MB to 80 MB.
Further refinements to the Semi-Annual Channel Server Core cut the size from 5 GB to just under 2 GB. Admins can use Server Core for various server roles, such as DNS server and Active Directory Domain Services.
Microsoft changed the default settings for the SMB1 protocol to uninstalled by default and tightened security around the newer SMB protocols.
Version 1709 is also more Linux-friendly. Microsoft added support for Linux containers, so they can run on the same system alongside Windows containers. To manage Linux containers, Microsoft added its Windows Subsystem for Linux -- also referred to as Bash on Windows -- feature, which had only been available in Windows 10 until the Windows Server 1709 release.
This post from Microsoft has a complete rundown of all the new features.
How do admins test features before a channel release?
Microsoft's Semi-Annual Channel poses serious challenges for IT professionals. A business accustomed to the Long-Term Servicing Channel release cadence will decide whether or not to use a newer version. But this is not the case with short-term cycles of every six months.
Organizations that subscribe to the Semi-Annual Channel require a more stringent testing approach before each new Windows Server release moves to production. The 18-month support cycle leaves little latitude to delay subsequent rollouts.
The Windows Insider Program enables IT pros to test and comment on the new features and functionality of an upcoming Semi-Annual Channel release. This helps admins try preview builds in their labs to check performance, verify compatibility with applications and tools and plan for any infrastructure changes, such as more storage or additional network bandwidth.
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