Microsoft KB Archive/224512

= FRS Builds Full-Mesh Replication Topology for Replicated DFS ROOT and Child Replicas =

Article ID: 224512

Article Last Modified on 2/23/2007

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APPLIES TO


 * Microsoft Windows 2000 Server
 * Microsoft Windows 2000 Advanced Server
 * Microsoft Windows 2000 Datacenter Server

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This article was previously published under Q224512



SUMMARY
The File Replication service (FRS) is a multi-threaded, multi-master replication engine that replaces the LMREPL service included in Microsoft Windows NT versions 3.x and 4.0. Windows 2000 domain controllers and servers use FRS to replicate system policy and login scripts for Windows 2000 and down-level clients. However, because system policy and login script replication is performed by Active Directory replication, it is not affected by the following information.

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

This article describes the replication topology generated by FRS and how to modify the default topology.



MORE INFORMATION
FRS builds a full-mesh replication topology between all Windows 2000 computers hosting a replicated piece of the DFS namespace.

Viewed graphically, the default replication topology is similar to a fully trusted domain model, in which the NTFRS connection objects are analogous to two-way trusts. The number of default connection objects can be determined using the following formula

Number of NTFRS connection objects = ( *(n-1))

where  is the number of Windows 2000 domain controllers or member servers enabled for replication in the Distributed File System snap-in for a portion of the DFS namespace. For example, if four domain controllers in the A.COM domain are configured to replicate the fault-tolerant root, every server would have an NTFRS connection to every participating server, for a total of 12 connection objects.

Enabling DFS Replication
DFS replication is not enabled by default. To enable, disable, or view the DFS replication settings:
 * 1) Start the Distributed File System Manager snap-in (Dfsgui.msc).
 * 2) Right-click the level of the DFS tree "backed" by more than one Windows 2000 computer in the left pane, and then click Replication Topology.
 * 3) Click Enable or Disable as required.

Enabling or disabling replication creates corresponding connection objects in the Active Directory to facilitate the replication of DFS content between partners. DFS child replicas whose shares reside on partitions that do not use the version of the NTFS file system included with Windows 2000 display "N/A" in the Replicate column of the Enable Replication dialog box.

Modifying the DFS Replication Topology
Wide-area networks typically consist of faster network connections between major computing hubs and slower links connecting branch offices. Administrators wanting to fine-tune the DFS replication topology to better suit their network infrastructure can delete NTFRS connection objects in the Active Directory Users and Computers snap-in, or directly in the Active Directory, using a suitable tool such as Ldp.exe.

To view NTFRS connection objects in the Active Directory from the user interface:  Click Advanced Features on the View menu of the Active Directory Users and Computers snap-in (Dsa.msc).  In the left pane, navigate to the following level: System File Replication Service DFS Volumes DFS Root container  DFS connection objects are displayed in the right pane for each level of the DFS namespace in which DFS replication has been enabled in the Distributed File System Manager snap-in (Dfsgui.msc). Type the name of the GUID labeled connection object in the description field by:  Viewing the properties for any connection in the right pane, and then clicking the member link Change button. Again, viewing the properties for the connection object and typing the name of the Computer Link box in the Description box. Repeat as required.</li></ol> </li></ol>

Viewing DFS Connection Objects in the DS
The GUIDs for DFS connection objects belong to the NTDSConnection object class. Connection objects can be viewed directly in the DS using the ADSI Edit snap-in or an equivalent application.

For a domain controller in the A.COM domain hosting a fault-tolerant DFS root namespace named "DFSFT" and a child node replica named "TOOLS," the path in DS is:

CN={59ec0127-ccdf-11d2-8fd1-00c04f8f4f54},CN={d42a1614-cd9e-11d2-8fd2-00c04f8f4f54},CN=DFSFT|tools,CN=DFSFT,CN=DFS Volumes,CN=File Replication Service,CN=System,DC=a,DC=com'

Where:

DC=A,DC=COM is the the A.COM domain.

CN=DFSFT is the root of the DFS namespace and NTFRSReplicaSet.

CN=DFSFT|tools is the DFS root name and tools is a DFS child node.

CN={d42a1614-cd9e-11d2-8fd2-00c04f8f4f54}is the GUID for the NTFRS member.

CN={59ec0127-ccdf-11d2-8fd1-00c04f8f4f54}is the GUID for the nTDSConnection.

Recovering from Link Failures
The Distributed File System snap-in lacks the functionality of the Active Directory Knowledge Consistency Checker (KCC) to evaluate and generate new connection objects to re-enable connectivity. If the replication topology is significantly modified, perhaps to the point of a single point of connectivity, the failure of a critical link, computer, or system could prevent, or seriously delay, replication between two computers and their dependents until the problem is resolved. An administrator may need to intervene as a surrogate KCC.

The Distributed File System snap-in lacks detail in modifying the replication topology; replication is either off, or a full inbound mesh is created from the selected computers perspective in Dfsgui.msc.

The method of resolution depends on the replication schedule, importance of data consistency, content change rate, problem source, and amount of deviation away from the default topology.

If replication is beyond repair and not likely to return due to a total and unrecoverable replica partner, disable replication for all computers in a given namespace using Dfsgui.msc, re-enable replication for the appropriate level of the DFS namespace, then prune the connection objects in Dsa.msc as appropriate.

Pruning Connections as New Replicas Are Added
Additional pruning may be required as new computers are added to a replica namespace because enabling replication only builds a full-mesh topology for the new computer.

Additional query words: FRS NTFRS

Keywords: kbenv kbinfo KB224512

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