Active Directory 32K Page Size
What is the Active Directory 32K page size?
Windows Server 2025 added a new optional 32K page size feature to the Active Directory database. Prior to Windows Server 2025, the database page size was 8K bytes. The 32K page size allows an AD object to hold up to approximately 3200 entries, compared to approximately 1200 entries for an 8K page.
Exceeding the entry limit triggers LDAP_ADMIN_LIMIT_EXCEEDED.
Page Modes
Windows Server 2025 can operate in one of three modes:
- 8K page mode
- 8K page simulation mode with 32K physical pages
- 32K page mode
The 8K page mode operates the same as in previous versions of Windows Server. It is the default mode if you upgrade a server in-place from Windows Server 2022 to Windows Server 2025.
The 8K page simulation mode is the default for a new installation of Windows Server 2025. The 8K pages are mapped into 32K physical pages. The remaining 24K bytes are left unused on each page.
The 32K page mode uses the entire physical page.
32K Page Mode
The 32K page mode can be enabled only when all of the following conditions are met:
- The AD domain functional level has been successfully raised to Windows Server 2025.
- The AD forest functional level has been successfully raised to Windows Server 2025.
- All the domain controllers in the AD forest are running Windows Server 2025 or later. (This is enforced by successfully raising the AD forest functional level to 2025.)
- The AD forest is stable, with replication working reliably between all domain controllers.
Enabling the 32K page feature is irreversible. You cannot restore AD from an old backup that was created prior to enabling 32K pages.
Mixing 8K page backups is okay
It is okay to mix backups created in 8K page mode with backups created in 8K simulation mode.
Bug in System State Recovery
There is a bug in Windows Server 2025 when using 8K page mode. If you try to create a System State backup, the backup will contain corrupt data. If you attempt to restore the DC from the System State backup, it will cause a Blue Screen of Death (BSOD) with error code 0xC0002e2 (STATUS_DS_INIT_FAILURE).
Use U-Move to test
You can use U-Move to create a test network to allow you to test 32K page mode prior to deployment.
For more information
For more information, see the following topics:
- Database 32k pages for Active Directory (Microsoft Learn)
- Enable Database 32k pages optional feature in Active Directory Domain Services (Microsoft Learn)
| U-Move for Active Directory |
