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Want an Effortless Windows Server 2025 Upgrade? Why You Must Understand the New 32k Page Size Benefit.
Windows Server 2025 introduces a significant update to Active Directory (AD). The database that powers AD can now use a larger “page size.” Think of the database as a large book; the page size has increased from 8KB to 32KB. This change allows AD to handle larger data entries and overcomes some long-standing limitations. While this is a welcome improvement, it also creates a hidden problem for system administrators who upgrade existing servers directly.
The In-Place Upgrade Trap
The core issue arises from how you move to Windows Server 2025. If you perform an “in-place upgrade”—installing the new operating system over an old one—the Active Directory database does not automatically switch to the new 32KB page size. It remains at the old 8KB size for compatibility.
This creates a mismatch that you might not notice at first. The server will appear to run correctly, but it is not gaining the benefits of the new database structure. This hidden discrepancy can lead to unexpected problems in the future as Microsoft builds new features that rely on the 32KB page size.
Why This Mismatch is a Problem
An Active Directory “forest” can only use the 32KB page size feature if every single domain controller (DC) in that forest supports it. If even one DC is running with the old 8KB page size, the entire feature cannot be enabled. This includes older servers and new Server 2025 machines that were created through an in-place upgrade. You are left with a system that is not fully modernized and may be difficult to troubleshoot later.
The Recommended Upgrade Path
Microsoft’s own guidance, supported by experts, advises against in-place upgrades for domain controllers. The safer and more effective method is to build a brand new Windows Server 2025 machine from scratch.
Follow this process:
- Install Windows Server 2025 on a new server.
- Promote this new server to a domain controller in your existing forest. It will automatically be created with the new 32KB database page size.
- Transfer all necessary roles and data from an old DC to the new one.
- Demote and decommission the old domain controller.
By replacing old DCs with new ones instead of upgrading them, you ensure your entire AD environment is modern, consistent, and ready for the future.