Windows 2000 Server uses File Replication Service (FRS) to replicate information stored in the system volume (\sysvol) directory. Win2K also uses FRS to synchronize Distributed File System (Dfs) replica sets. FRS replaces Windows NT's LMRepl service. FRS is important to a discussion of Active Directory (AD) replication for two reasons.

First, because the \sysvol share needs to be replicated to all domain controllers (DCs), it too requires a replication topology. To keep things simple, FRS adopts the replication topology that the Knowledge Consistency Checker (KCC) creates for AD. The exception to this rule is Dfs replica sets, which you configure through the Microsoft Management Console (MMC) Dfs snap-in. The replication of directory objects in AD is separate from the replication of \sysvol. One of the differences is that directory data replicated between sites is compressed, but files replicated from \sysvol aren't compressed.

Second, FRS is important to Group Policy. Group Policy Objects (GPOs) have two physical components—a Group Policy Container (GPC) and a Group Policy Template (GPT). The GPC resides in AD and contains all the property settings defined for the GPO. The GPT resides under \sysvol in a folder whose name matches the policy's globally unique identifier (GUID), as Figure A shows. This folder contains information about security settings, administrative template-based policies, script files, and any applications that Win2K is publishing or advertising through the policy.

If the GPC and GPT versions of the policy aren't synchronized—for example, if the two parts replicated separately at different times or if one part of the GPO is present but the other isn't—Win2K won't apply that GPO. Such errors, which appear in the Application log as IDs 1000 and 1001, report that Win2K can't propagate the GPO because it can't find the GPT portion in \sysvol. You can use the Group Policy Verification Tool (gpotool.exe) to troubleshoot this problem. Gpotool queries each DC and determines which policies are present on the DC, which version of a given policy the directory contains, and which version of a given policy the \sysvol folder contains. Gpotool reports on any mismatches that occur between these versions.