FRS Polling of the AD May Delay DFS or SYSVOL Replication for 10 Minutes or More (221105)

SUMMARY

The File Replication service (FRS) is a multi-threaded, multi-master replication engine that replaces the LMREPL service in the 3.x/4.0 versions of Microsoft Windows NT. Windows 2000 domain controllers and servers use FRS to replicate system policy and login scripts for Windows 2000 and down-level clients.

FRS can also replicate content between Windows 2000 servers hosting the same fault-tolerant DFS roots or child node replicas.

This article describes how FRS polls the Windows 2000 Active Directory for configuration changes, and its impact on the replication of files and folders in the DFS and SYSVOL trees.

MORE INFORMATION

FRS polls the Active Directory at regular intervals for configuration and subscriber list changes. Each time a Windows 2000 server is started or the NTFRS service is started, the computer object in the DS is polled in eight short intervals followed by eight long intervals, provided no configuration changes take place.

For domain controllers, the default short and long intervals are 5 minutes each. Member servers also have a 5 minute short interval, but a 60 minute long interval.

With each FRS reset event, the eight short and eight long polling cycle is invoked again.

The settings for the short and long polling intervals are located in the Hkey_Local_Machine\SYSTEM\CurrentControlSet\Services\NTFRS\Parameters section of the registry.

Entry	Default
DS polling short interval in minutes (REG_DWORD)	5
DS polling long interval in minutes (REG_DWORD)	5 minutes on DCs, 60 on servers

The FRS service waits two polling intervals, short or long, before replication takes place. Long polling intervals occur only after eight short polling intervals have finished without change.

Events that reset the polling interval include:

Replicas added
Replicas deleted
Connection added
Connection deleted
Schedule changed
File or folder filter change

Because of this, replication will never occur if an FRS reset event takes place at 4 minute intervals or at any period less than the current value for DS Polling Short.

The worst-case scenario assuming a change to the steady state for a member server is to have a single change occur 59+ minutes into a long polling interval, and then wait two more short intervals for replication to occur for a total of approximately 70 minutes. The worst-case scenario for a domain controller is approximately 15 minutes.

Sample polling events in the Ntfrs_000x.log file in the %SystemRoot%\Debug folder are shown below

<PollDs: 1144: 9284: S4: 18:00:19> :Nd: Begin merging Ds with Db
<PollDs: 1144: 9286: S4: 18:00:19> :Nd: End merging Ds with Db
<DsCsMain: 1144: 9574: S4: 18:05:19> :Nd: Polling the DS in 5 minutes