Directory Replication

by Wayne Maples [Published on 20 April 2004 / Last Updated on 20 April 2004]

Replication is the process of duplicating a directory and its contents from an export server to any number of import servers. With NT Server as the export server, NT Server, NT Workstation and LAN Manager servers can be import servers.

The Replication service is not enabled by default.

Data placed in an export server's export directory will be duplicated (replicated) to all import servers' import directories. NT's default for the export and import directories are:

\Winnt\System32\Repl\Export\

\Winnt\System32\Repl\Import\

These directories are under the control of the Replication service. The service performs whatever actions are necessary to ensure that the import directory tree matches the export directory tree. For example, files deleted from the export directory tree will be removed from the import directory. Only subdirectories under the export directory will be replicated, not files in the export directory itself, that is the Export root directory, \Winnt\System32\Repl\Export\.

A standard default standard directory in the replication root is named "Scripts". This is where logon scripts are placed. The NetLogon share points to the \Import\Scripts directory. This makes defining user profiles easy by allowing the general share name to proceed the script name, such as "NETLOGON\wmaples.bat."

To get replication working:

  • Apply current SP
    You should understand that the replication service for NT was broken out of the box until SP3. I recommend SP6a or later.
  • Create an account to run the replication service
    The account must be named repluser and it must be a member of the Replicator group.
  • Service parms
    Set the Directory Replicator service under Control Panel, setting the Directory Replicator service to startup type=Automatic, Logon As=repluser.
  • Server Manager
    Open the Properties dialog box for the export or import server (by double-clicking the computer name), and click the Replication button. If the server is an export server, select the Export Directories radio button. The default directory will appear in the From Path field. If the server is an import server, select the Import Directories radio button. The default directory will appear in the To Path field. My experience strongly suggests leaving these defaults asis.
  • Click Add under Export or Import, and select the computer to export to or import from.
  • Place scripts or other files in the Export directory.
  • Reboot all export and import servers.

Keys that control windows nt domain controller directory replication.
How often export server looks for changes in replicator folders:

Hive: HKEY_LOCAL_MACHINE
Key: SYSTEM\CurrentControlSet\Services\Replicator\Parameters
Type: REG_DWORD
Name: Interval
Value: value in minutes
min=1, Default=2, maximum=60

How long export folder must remain unmodified before replication to import servers:

Hive: HKEY_LOCAL_MACHINE
Key: SYSTEM\CurrentControlSet\Services\Replicator\Parameters
Type: REG_DWORD
Name: GuardTime
Value: value in minutes
min=0, Default=2, maximum= 1/2 value of Interval

Number of times import server repeats the change notice after initial announcement:

Hive: HKEY_LOCAL_MACHINE
Key: SYSTEM\CurrentControlSet\Services\Replicator\Parameters
Type: REG_DWORD
Name: Pulse
Value: # of times
Default=2 times. Max time import servers wait before requesting an update:

Hive: HKEY_LOCAL_MACHINE
Key: SYSTEM\CurrentControlSet\Services\Replicator\Parameters
Type: REG_DWORD
Name: Random
Value: # of seconds
Default=60 seconds, legal range 1 - 120 seconds.

Some gotcha!s:

Replication will halt if an application is accessing or viewing the export or import directories. The Replication service can not know if files are being changed. It is designed to wait until files and directories are inactive before replicating.

Replication will only occur between computers with system clocks set within 59 minutes of each other. Lets say you set two servers to the correct time and date. They may be side-by-side. Should you not have set the time zone, and they have different time zones, then replication will fail because they will have times set > 59 minutes difference. Everyone checks date/time on servers. Fair number don't check timezone setting.

Although Microsoft documentation stated that replication service was of general utility, only use it for built in NT functionality. Don't try to replicate data or word processor files or such. It will clog your network. To replicate those kinds of files, create scripts and use xcopy or scopy driven by the scheduler.

Don't get confused. Export to the import directory on your export server.

Featured Links