RAS-Connected BDCs/PDC's: Full_Sync Replication Times (120487)

MORE INFORMATION

Following are the test results from two separate test runs of a Full_Sync forced on a single Remote Access Service (RAS)-attached Backup Domain Controller (BDC) across a 9600-baud null-modem connection:

• 9200-user/500 group Security Account Manager (SAM) replicated (full_sync) in 22 minutes.
• 9200-user/50 group (all groups populated) SAM replicated (full_sync) in 36:10.
  
  NOTE: Most of the delay is when the BDC made its API call to the Primary Domain Controller (PDC) to get the next several accounts. The delay for each call was minimal (for example, 37 seconds to return 201 accounts).

A BDC can be connected to a remote domain through RAS and a modem connection. However, if the RAS-connected BDC is ever expected to be promoted to PDC while it is remotely connected to the domain, this BDC should be set up as a dial-out - only RAS client (RAS is not running on this computer). If you promote the RAS-connected client, Netlogon stops, changes roles, and restarts. RAS is dependent on Netlogon, so when Netlogon stops, you would lose your connection. By just having the RAS client dial- out services on this remote BDC, it can then function as a PDC if desired because that functionality does not depend on Netlogon running constantly. If neither the RAS server (which could also be a BDC) nor the RAS-connected BDC will be expected to ever serve as PDC, this is not an issue. A RAS- connected BDC that has been promoted to PDC functions as it should, but possibly with slower response time, depending on line speed.

If a remote site has a RAS-connected BDC that dials in nightly to do a partial synchronization of any changes, and on some days 2,000 changes are made to the SAM/LSA database, then the default ChangeLogSize should be increased. This may be necessary if any BDC has been offline while a lot of changes have occurred, or else this BDC may be forced to do a full synchronization of the database. If minimal changes (for example, fewer than 2,000) occur during the time the RAS BDC or any BDC does not have a physical connection to the PDC, then the default size is sufficient. If an administrator begins to notice any BDCs doing full synchronizations, it could be that many changes are occurring and the ChangeLogSize needs to be increased. The default ChangeLogSize is 64K which is approximately 2,000 changes.

NOTE: A single UI operation (such as adding a user) results in multiple changes; allow room for this in your calculations.

Registry Changes

Use REGEDT32.EXE to make the following changes to the Registry on ONLY the PDC of the domain. Changes can be made at to the ChangeLogSize as long as the range is between (64K to 4 MB - decimal). You need to reboot your computer for the changes to take effect.

Add the following value:


HKEY_LOCAL_MACHINE

Key Name: SYSTEM\CurrentControlSet\Services\NetLogon\Parameters
Name: ChangeLogSize
Type: REG_DWORD
Data (New): 128000 (Decimal)