Ever since Microsoft began delivering feature updates to Windows as "a service," Windows client officials have been reticent to use the "release to manufacturing" (RTM) phrase -- even when they've settled on a particular build that they'll christen as a new feature release. The Windows Server team seemingly doesn't have the same hang-up. In fact, the Server team has acknowledged that Windows Server 2019 is the first Server build where Microsoft intentionally skipped RTM.
I missed this official acknowledgement, but lately, a couple of readers have been asking about it. I found a Microsoft blog post explaining the decision not to RTM Windows Server 2019 thanks to an October 3 blog post on Redmond Magazine's site.
Microsoft officials did declare Windows Server 2019/Windows Server 1809 was generally available on October 2, the same date that the Windows 10 October 2018 Update/Windows 10 1809 hit general availability (GA). (Since then, Microsoft has pulled both 1809 client and server because of customer reports of data loss after installing 1809. As of the morning of October 19, Microsoft still has not re-released 1809 client or server to mainstream customers.)
For Server customers, Microsoft made Windows Server 2019/1809 available briefly -- after a few hours of customer reports of download problems -- on its Volume Licensing Service Center (VLSC) and Azure Marketplace. Microsoft officials said at that time the plan was to make Windows Server 2019/1809 available on Visual Studio Subscriptions (formerly known as MSDN) and other portals like the Microsoft Partner Network (MPN) portal later on in October.
In a separate blog post on October 2 on the "Storage at Microsoft" blog, Microsoft officials disclosed that the Windows Server 2019 released skipped RTM and went straight to GA for the first time in Windows Server history. The stated reason: More and more customers are deploying Windows Server in the cloud and not via on-premises servers loaded with fresh bits.
From that blog post:
"Windows Server 2019 is the first version to skip the classic Release To Manufacturing (RTM) milestone and go directly to General Availability (GA). This change is motivated by the increasing popularity of virtual machines, containers, and deploying in the cloud. But it also means the hardware ecosystem hasn't had the chance to validate and certify systems or components before the release; instead, they start doing so today."
(A related aside: Microsoft officials recently disclosed that 50 percent of virtual machines on Azure are running Linux, not Windows Server.)
Microsoft officials said they expected Windows Server 2019 to be loaded on certified servers in mid-January, and that they'd have a Windows Server Software Defined (WSSD) launch event around that time.
In the interim, Microsoft is displaying a warning against deploying Windows Server 2019 in production to anyone attempting to use features unique to Windows Server 2019, such as updated Storage Spaces Direct or Software Defined Networking, and is requiring an extra step to configure. Customers also have the option to build their own servers running these features right now using components from the Windows Server catalog.
Speaking of Windows Server 2019, here's a handy chart from the "Microsoft 365 Powered Devices Australia" blog that compares the features available in Windows server 2019 Standard vs. Windows Server 2019 Datacenter Editions.