Microsoft has fixed a known issue causing “boot device inaccessible” errors during startup on some Windows Server 2025 systems using iSCSI.
“This is observed on servers operating under NDIS Poll Mode booting from an iSCSI LUN,” the company explained when it acknowledged the bug in late October.
“Under such configuration, the server will experience the error during startup, after the installation of Windows Server 2025 is completed.”
The iSCSI protocol (short for Internet Small Computer Systems Interface) is a built-in Windows Server component that allows servers to connect to remote storage devices over TCP/IP networks using SCSI commands.
This allows them to use remote storage (often hosted on a SAN or Storage Area Network) like a local disk, making iSCSI ideal for use in centralized storage, virtualization, and data center environments.
“This issue was resolved by Windows updates released February 11, 2025 (KB5051987), and later,” the company said in an update to the Windows release health dashboard.
“We recommend you install the latest update for your device as it contains important improvements and issue resolutions, including this one.”
The KB5051987 cumulative update also fixes bugs causing USB audio and camera problems after installing the January 2025 security updates.
In November, Redmond addressed another series of bugs that were triggering install, upgrade, and Blue Screen of Death (BSOD) issues on Windows Server 2025 devices with a high core count, and one month later, a known issue causing boot failures on some Windows Server 2022 systems with two or more NUMA nodes.
Windows Server 2025 (the Long-Term Servicing Channel/LTSC release for Windows Server) reached general availability in early November, with a free 180-day trial available via the Microsoft Evaluation Center.
Microsoft released the first Windows Server 2025 build for admins in the Windows Insider program in January, introducing hotpatching, next-gen Active Directory, and support for ‘SMB over QUIC’ alternative ports.