Q160513: Alternatives to the Directory Replicator Service

Article: Q160513
Product(s): Microsoft Windows NT
Version(s): 3.5 3.51 4.0
Operating System(s): 
Keyword(s): kbenv
Last Modified: 09-AUG-2001

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The information in this article applies to:

- Microsoft Windows NT Workstation versions 3.5, 3.51, 4.0 
- Microsoft Windows NT Server versions 3.5, 3.51, 4.0 
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SUMMARY
=======

Microsoft Windows NT provides a service that is designed to replicate logon
scripts between domain controllers in a domain. Logon scripts were first
introduced with the Microsoft LAN Manager product, and, although Windows NT
provides peer-level server capabilities and user profiles that provide far more
configurability of the desktop and user settings, logon script replication is
still supported for command-line execution and down-level clients.

The alternatives mentioned in this article resolve several issues with the
Replicator service, such as:

- An arbitrary number of parent directories can be exported.

- Very large file and directory synchronizations can be replicated, which may
  have overwhelmed the directory replicator service.

- Exclusive access is not needed to the entire directory so a process such as
  File Manager or Explorer will not interfere with replication simply by having
  a window open in the Export directory.

MORE INFORMATION
================

The Microsoft Resource Kit provides a robust copy utility called Robocopy.exe.
This utility can be used for very large transfers and synchronizations with
large amounts of data and individual files. This command can be launched in
several ways, and below are some methods that can be used as alternatives to the
Replicator service.

For more information on the Robocopy.exe command, see the online help (type
"robocopy /?") and the Robocopy.wri file included in the Resource Kit. Below is
a summary of the syntax used in this document.

ROBOCOPY v 1.54  :  Robust File Copy for Windows NT
---------------------------------------------------

Usage : ROBOCOPY source destination [file [file]...] [options]
source : Source Directory (drive:\path or \\server\share\path).
destination : Destination Dir (drive:\path or \\server\share\path).
file : File(s) to copy (names/wildcards - default is "*.*").
/S : copy Subdirectories, but not empty ones.
/E : copy subdirectories, including Empty ones.
/R:n : number of Retries on failed copies - default is 1 million.
/W:n : Wait time between retries - default is 30 seconds.
/REG : Save /R:n and /W:n in the Registry as default settings.
/X : report all eXtra files, not just those selected.
/V : produce Verbose output, showing skipped files.
/L : List only - don't copy, timestamp or delete any files.
/ETA : show Estimated Time of Arrival of copied files.
/MOVE : Move files and dirs (delete from source after copying).
/PURGE : delete dest files/dirs that no longer exist in source.

Method 1
--------

A batch file can be created and simply run when changes have been made to the
source files and synchronization is needed between the domain controllers. An
example of such a batch file is below. Because of word- wrap, each grouping of
lines is actually one line in the ASCII BAT file.

  robocopy \\<computer1>\admin$\system32\repl\export\ 
  \\<computer1>\admin$\system32\repl\import /s /v /r:1 /w:1 /eta

  robocopy \\<computer1>\admin$\system32\repl\export\ 
  \\<computer2>\admin$\system32\repl\import /s /v /r:1 /w:1 /eta

NOTE: <computer1> and <computer2> are the names of the computers
being synchronized.

Method 2
--------

The above BAT file can be made to run in a loop, pausing for a specified amount
of time between each copy. Another Resource Kit utility called Sleep.exe can be
used to specify the number of seconds for the delay between synchronizations.
This BAT file could be placed in the Startup group, always run, and minimized on
the desktop. To ensure access to each remote domain controller, Sleep.exe should
be run under the user context of an administrator. Below is an example of such a
BAT file. Because of word- wrap, each grouping of lines is actually one line in
the ASCII BAT file.

  :loop

  robocopy \\<computer1>\admin$\system32\repl\export
  \\<computer1>\admin$\system32\repl\import /s /v /r:1 /w:1 /eta

  robocopy \\<computer1>\admin$\system32\repl\export
  \\<computer2>\admin$\system32\repl\import /s /v /r:1 /w:1 /eta

  sleep 1800

  goto loop

NOTE: <computer1> and <computer2> are the names of the computers
being synchronized.

If file permissions must be maintained on the files, use SCOPY, another resource
kit utility. As Robocopy is more robust, Scopy could be used for the initial
replication of NTFS permissions, and then Robocopy can be used for the regular
replication, if the permissions are not changed on a regular basis and the
directory tree structure is fairly static.

If less granular permissions are acceptable, move away from NTFS file security
and towards the lower granular security implemented with share permissions. This
may reduce the amount of administration required and eliminate the need for
replicating file permissions.

Method 3
--------

Another method to maintain directory structures remotely can be to schedule a
batch file using the Scheduler service. Services provide the benefit of allowing
for synchronization independent to the user logged on, and when a user is logged
on, there is no minimized icon that could be accidentally terminated. As with
any access to a remote machine over the network, the user-context of the process
must have the necessary read or write permissions. To do this, the Scheduler
service needs to be started with a user account instead of the local system
account. If more than one synchronization is desired each day, each occurrence
requires a separate statement. The BAT file presented in Method 1 above can be
used as an example, and the following statements can be used to configure the
Scheduler service to establish synchronization at the desired intervals.

  AT 12:00AM /every:m,t,w,th,f,sa,su c:\bin\replicate.bat
  AT 08:00AM /every:m,t,w,th,f,sa,su c:\bin\replicate.bat
  AT 12:00PM /every:m,t,w,th,f,sa,su c:\bin\replicate.bat
  AT 08:00PM /every:m,t,w,th,f,sa,su c:\bin\replicate.bat

With the /every switch, the Scheduler service records the frequency and initiates
the jobs with no more administrator intervention.

To verify the status of the Scheduler service, type AT at the command prompt.

To test the BAT file with the Scheduler service, the /interactive switch can be
use to see output from Robocopy, or the output can be redirected to a file as
mentioned below.

Method 4
--------

In the interest of completeness, one final method can be discussed. The BAT file
displayed in Method 2 above, which uses the SLEEP command to regulate the
synchronization interval, can be launched as a user created service. This
provides the usual benefits of running as a service, and also the benefit of
there being a single thread of execution with the single BAT file. Although
unlikely, if the Scheduler service were used to regulate the interval instead of
the SOON command, and if Robocopy were to fail during the file synchronization,
launched processes could accumulate without completing, as the Scheduler service
does not track launched processes after they are run. The BAT file in Method 2
could be used along with the Instsrv.exe command to create the registry entries
for the Srvany.exe service from the Resource Kit. See online help and the
Resource Kit Help file for the particular syntax and instruction.

Robocopy Notes
--------------

- The /purge command can be used to delete files on the destination server that
  have been deleted from the source server. This is the behavior of the
  replicator service. Use this switch with caution because it deletes data.

- If the destination files you are trying to replicate are often in an open
  state, you may want to limit the default number of retires Robocopy will try
  when copying these files. Using the switches "/R:5 /W:5" will timeout more
  quickly.

- Robocopy displays very detailed output that administrators may find useful
  and want to save to a file. This output can be redirected to a file by
  appending the following symbolic path to each ROBOCOPY statement:
  ">>drive:\directory\filename.txt." In a relatively short time, this may
  create a very large file. Even if few changes occur on the source server and
  synchronization checks occur every 30 minutes, this file can grow to an
  estimated size of about 4.5 MB in only a month. This assumes that 3 KB of
  information is written for each replication attempt, and the verbose switch
  is not used.

- Unlike the Replicator service, Robocopy does not have to run on the server
  where the source files are located.

- If absolute symmetry is needed between the source and destination directory
  structure, the /purge, /e, /t, and event /is switches can be used. This level
  of duplication is probably not necessary. See the online help and the
  Robocopy.wri file for more details.
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Keywords          : kbenv 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT351search kbWinNT350search kbWinNT400search kbWinNTW350 kbWinNTW350search kbWinNTW351search kbWinNTW351 kbWinNTSsearch kbWinNTS400search kbWinNTS400 kbWinNTS351 kbWinNTS350 kbWinNTS351search kbWinNTS350search
Version           : 3.5 3.51 4.0

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