Recipe 16.11 Determining How Much Whitespace Is in the DIT

16.11.1 Problem

You want to find the amount of whitespace in your DIT. A lot of whitespace in the DIT may mean that you could regain enough space on the disk to warrant performing an offline defrag.

16.11.2 Solution

16.11.2.1 Using a graphical user interface

Run regedit.exe from the command line or Start Run.
Expand HKEY_LOCAL_MACHINE SYSTEM CurrentControlSet Services NTDS Diagnostics.
In the right pane, double-click on 6 Garbage Collection.
For Value data, enter 1.
Click OK.

16.11.2.2 Using a command-line interface

> reg add HKLM\System\CurrentControlSet\Services\NTDS\Diagnostics /v "6 Garbage[RETURN] 
Collection" /t REG_DWORD /d 1

16.11.2.3 Using VBScript

' This code enables logging of DIT whitespace information in the event log.
' ------ SCRIPT CONFIGURATION ------
strDCName = "<DomainControllerName>"  ' e.g. dc1
' ------ END CONFIGURATION ---------

const HKLM = &H80000002
strNTDSReg = "SYSTEM\CurrentControlSet\Services\NTDS\Diagnostics"
set objReg = GetObject("winmgmts:\\" & strDCName & "\root\default:StdRegProv")
objReg.SetDWORDValue HKLM, strNTDSReg, "6 Garbage Collection", 1
WScript.Echo "Garbage Collection logging set to 1"

16.11.3 Discussion

By setting the 6 Garbage Collection diagnostics logging option, event 1646 will get generated after the garbage collection process runs. Here is an example 1646 event:

Event Type:        Information
Event Source:        NTDS Database
Event Category:        Garbage Collection 
Event ID:        1646
Date:                5/25/2003
Time:                9:52:46 AM
User:                NT AUTHORITY\ANONYMOUS LOGON
Computer:        DC1
Description:
Internal event: The Active Directory database has the following amount of free hard 
disk space remaining. 
 
Free hard disk space (megabytes):
100
Total allocated hard disk space (megabytes):
1024

This shows that domain controller dc1 has a 1 GB DIT file with 100 MB that is free (i.e., whitespace).