Windows Server vNext Preview Build 29621 is out, here's what's new

Windows Server vNext Insider build 29621 introduces Trusted Launch VMs, Quick Machine Recovery, ReFS Boot, and NVMe-over-Fabrics support.

Microsoft released Patch Tuesday updates for Windows 11 and Windows 10 ESU with hundreds of security fixes, along with Security Updates (SUs) for Exchange Server Subscription Edition (SE), 2016, and 2019. However, another release that may have flown under the radar is for Windows Server vNext Insider Preview build 29621, now available.

The latest release of the Windows Server Long-Term Servicing Channel (LTSC) Preview contains both the Desktop Experience and Server Core installation options for Datacenter and Standard editions and Azure Edition (for VM evaluation only). There are tons of new features in tow too.

The highlight is Trusted Launch for VMs, a security upgrade that we have already covered in detail here. Another enhancement in the same vein is Quick Machine Recovery (QMR), which was announced for consumer builds of Windows 11 over a year ago. As the name implies, this feature enables devices to recover from boot errors by automatically searching for cloud-based remediations and applying them from the Windows Recovery Environment (WinRE), without requiring IT admins to intervene and apply complex workarounds. QMR is also a component of the Windows Resiliency Initiative (WRI), and a Group Policy option will become available in upcoming builds to toggle its behavior.

Additionally, Resilient File System (ReFS) Boot is enabled, and NVMe-over-Fabrics (NVMe-oF) has also been rolled out. Here is how Microsoft describes it:

"NVMe-over-Fabrics (NVMe-oF) extends the NVMe protocol—originally designed for local PCIe-attached SSDs—across a network fabric. Instead of using legacy SCSI-based protocols such as iSCSI or Fibre Channel, NVMe-oF allows a host to communicate directly with remote NVMe controllers using the same NVMe command set used for local devices. In this Insider build, Windows Server supports:

• NVMe-oF over TCP (NVMe/TCP), allowing NVMe-oF to run over standard Ethernet networks without specialized hardware.
• NVMe-oF over RDMA (NVMe/RDMA), enabling low-latency, high-throughput NVMe access over RDMA-capable networks (for example, RoCE or iWARP) using supported RDMA NICs."

And here are some known limitations in this build:

• ReFS Boot systems create a minimum 2GB WinRE partition.
• When WinRE cannot be updated due to space constraints, the system may disable WinRE. Disabling WinRE does not remove the partition.
• If the WinRE partition is deleted and the boot volume is extended over it, this operation is unrecoverable without a clean install.

Finally, you can check out known issues from Microsoft's blog post and download build 29621 from here.

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Posted Thursday 16 July 2026 at 7:47 am AEST (my time).

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