Critical Issues in Windows Server 2025: Performance, Installation, and iSCSI Warnings

Microsoft has issued a critical warning regarding several significant issues identified in the latest iteration of its server operating system, Windows Server 2025. These problems, if left unaddressed, could lead to substantial disruptions for organizations relying on this platform, particularly those operating high-core systems and utilizing specific installation and boot configurations.

Installation Process Affected by Unintended English Text Display​

One of the foremost concerns highlighted by Microsoft pertains to the installation process of Windows Server 2025. Users initiating installations via external media, such as USB drives or CDs, using server media version 25100.1742 or newer, have reported instances where the setup text unexpectedly reverts to English. This glitch occurs specifically when the Multilingual User Interface (MUI) is enabled, aiming to support multiple languages during installation.

Impact on Multinational Deployments​

For organizations operating in non-English-speaking regions, this unintended shift to English can cause confusion and complicate the deployment process. The discrepancy between the chosen language settings and the actual display language may lead to misconfigurations or hinder the ability to follow installation prompts accurately. As a result, IT administrators may face increased challenges in setting up servers correctly, potentially delaying deployment schedules and affecting overall operational efficiency.

Severe Performance Issues on High-Core Systems​

Another critical issue identified affects high-core systems, particularly those equipped with 256 or more processors. Users have reported experiencing severe performance degradations, including:

• Blue Screens of Death (BSOD): Systems may encounter unexpected BSOD errors during routine tasks such as launching applications or initiating reboots.
• Prolonged Boot Times: Restarting servers can result in delays extending up to three hours, significantly impacting uptime and service availability.

Diagnostic Challenges​

These performance and stability issues manifest inconsistently, making them difficult to diagnose and troubleshoot. The unpredictable nature of the BSODs and extended boot times complicates the task for IT administrators who manage large data centers or high-powered systems, where uptime and reliability are paramount.

Recommended Diagnostic Steps​

To ascertain whether a system is affected, Microsoft advises administrators to perform a straightforward diagnostic check:

1. Access Task Manager: Press Ctrl + Shift + Esc to open the Windows Task Manager.
2. Navigate to Performance Tab: Click on the 'Performance' tab to view system metrics.
3. Verify Logical Processors: Check the number of logical processors listed. Systems reporting more than 256 logical processors are susceptible to the identified issues.

Interim Workaround​

While Microsoft works on a permanent solution, an interim workaround is available to alleviate some of the instabilities:

1. Limit Active Logical Processors:
   • Restart the server and access the UEFI setup during the boot process.
   • Adjust the core allocation settings to limit the active logical processors to 256 or fewer.
   • Confirm the total processor count and reboot the server.

By capping the number of active processors, organizations can mitigate the risk of encountering BSOD errors and reduce boot times, thereby enhancing system stability until an official fix is released.

Boot Failures in iSCSI Environments​

The third major issue reported affects servers utilizing Internet Small Computer Systems Interface (iSCSI) technology under certain configurations. Specifically, servers configured to boot from an iSCSI Logical Unit Number (LUN) in SDIS Poll Mode may encounter the following problem:

• Boot Device Inaccessible Error: Post-startup, the server may display an error indicating that the boot device is inaccessible, preventing the completion of the boot process. This renders the server unusable until the issue is resolved.

Implications for iSCSI Deployments​

For organizations leveraging iSCSI for network storage solutions, this boot failure poses a significant threat to system availability and data accessibility. The inability to successfully boot from the designated iSCSI LUN disrupts server operations, potentially affecting critical services and applications hosted on the affected systems.

Microsoft's Response and Ongoing Efforts​

In response to these critical issues, Microsoft has taken the following steps:

• Acknowledgment of Issues: Formal recognition of the identified problems affecting Windows Server 2025.
• Interim Workarounds Provided: Offering temporary solutions, such as limiting logical processors and adjusting installation methods, to mitigate immediate risks.
• Development of Permanent Fixes: Committing resources to develop and release comprehensive patches addressing the root causes of the identified issues.

Microsoft emphasizes the importance of promptly implementing the interim workarounds to maintain system stability and minimize operational disruptions while a permanent resolution is being formulated.

Recommendations for IT Administrators​

Given the severity of the reported issues, IT administrators managing Windows Server 2025 deployments are advised to take proactive measures:

1. Assess System Vulnerability:
   • Conduct diagnostic checks to determine if systems exceed the 256 logical processor threshold.
   • Identify servers utilizing iSCSI configurations that may be affected by boot failures.
2. Implement Interim Workarounds:
   • For high-core systems, adjust logical processor limits via UEFI settings.
   • Consider alternative installation methods or postponing deployments until the installation text display issue is resolved.
3. Monitor System Performance:
   • Keep a vigilant eye on system logs and performance metrics to detect early signs of instability or BSOD occurrences.
   • Establish contingency plans for rapid response in case of unexpected server failures.
4. Stay Informed on Updates:
   • Regularly check for updates and patches released by Microsoft addressing these specific issues.
   • Engage with Microsoft support channels for assistance and guidance on mitigating the impact of these problems.

Conclusion​

The identification of critical issues in Windows Server 2025 underscores the challenges inherent in managing complex server environments. Microsoft’s proactive warning and provision of interim solutions are essential steps in safeguarding system integrity and ensuring continuity of operations for affected organizations. IT administrators must act swiftly to implement recommended workarounds, monitor system health diligently, and remain informed about forthcoming fixes to navigate the current instability effectively. As Microsoft continues to develop permanent remedies, stakeholders can anticipate more robust and reliable performance in future updates of Windows Server.

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Source: Candid.Technology Microsoft warns of 3 major Windows Server 2025 issues