Overview

Microsoft has released a series of updates to resolve significant issues affecting Windows Server 2025, including Blue Screen of Death (BSOD) errors and installation failures. These problems primarily impacted servers with high core counts and those utilizing iSCSI technology.

Background

Windows Server 2025, Microsoft's latest Long-Term Servicing Channel (LTSC) release, introduced advanced features and security enhancements. However, shortly after its release, administrators reported critical issues:

  • High Core Count Servers: Systems with more than 256 logical processors experienced installation failures, prolonged boot times, and BSOD errors. (bleepingcomputer.com)
  • iSCSI Environments: Servers booting from an iSCSI LUN encountered 'boot device inaccessible' errors during startup. (bleepingcomputer.com)

Technical Details

High Core Count Servers:

The issues stemmed from the operating system's inability to handle configurations exceeding 256 logical processors. Symptoms included:

  • Installation or upgrade processes failing or hanging.
  • Extended boot or restart times, sometimes exceeding three hours.
  • BSOD errors during application launches or system restarts.
iSCSI Environments:

Servers using iSCSI technology, particularly those operating under NDIS Poll Mode and booting from an iSCSI LUN, faced startup errors post-installation, rendering the systems unbootable. (bleepingcomputer.com)

Resolutions

High Core Count Servers:

Microsoft addressed these issues in the November 12, 2024 update (KB5046617). Administrators are advised to install this update promptly. For those unable to update immediately, a temporary workaround involves limiting the number of logical processors to 256 or fewer by adjusting firmware settings. (bleepingcomputer.com)

iSCSI Environments:

The 'boot device inaccessible' error was resolved in the February 11, 2025 update (KB5051987). Installing this update is crucial for systems utilizing iSCSI boot configurations. (bleepingcomputer.com)

Implications for IT Administrators

These issues underscore the importance of timely updates and proactive system monitoring. Administrators should:

  • Regularly check for and apply Microsoft updates.
  • Monitor system performance, especially in high-core and iSCSI configurations.
  • Implement temporary workarounds when immediate updates aren't feasible.

Conclusion

Microsoft's prompt response to these critical issues highlights the company's commitment to system stability and security. IT professionals must remain vigilant, ensuring their systems are updated and configured correctly to prevent such disruptions.