DCPROMO Space Requirements for Active Directory Database and Log Files (222019)

SUMMARY

The file size requirement for the Active Directory database and log files is dependent on the number and type of objects in the domain database (or databases held by the forest if the computer is also serving as a global catalog server).

For example, at a minimum in an upgrade scenario, Domain Controller Promotion (DCPROMO) allocates 200 MB for the database (Ntds.dit) and 50 MB for the log file(s), or 250 MB if they are placed on the same logical drive. Rounding and size calculation errors may result in errors even when 250 MB of free space is available, requiring even more free drive space to be available.

MORE INFORMATION

Before running DCPROMO, consider the number of objects that are likely to reside in each domain in the Windows 2000 forest, along with their contribution to the global catalog.

When you are planning Active Directory size and performance requirements, consider the following items:

Active Directory databases are larger by some multiple than the SAM file on a Microsoft Windows NT 4.0 domain controller with the same number of objects.
The Active Directory database grows until deleted entries are tombstoned every 60 days.
Consider the effect that domain collapse scenarios and potential mergers will have on domain controllers in each Active Directory domain and global catalog server in the forest.
For maximum performance, the Active Directory database, Active Directory log files, and the Windows 2000 operating system should be placed on separate physical hard disks.
The SYSVOL should be placed on a different physical partition than the operating system, Active Directory database, and Active Directory log files to prevent its contents or staging files from consuming all available disk space. This could cause other components or Windows to fail or cause degradation in performance.
In a lab environment, it may be helpful to stage the operating system, Active Directory, and log files across separate partitions even on the same physical drive so that performance monitoring tools can be used to profile the amount and type of access (percent of disk read time, percent of disk write time, and bytes read or written per second) to each element.
To avoid "touch costs" for visits to domain controllers in remote offices, administrators may want to "oversize" domain controllers. Create Active Directory DIT and log files on domain controllers with hard disks with enough free space and memory to accommodate a worst-case growth scenario for a three-year timeframe.
To be safe, at least double your estimated size.