Create a Replication Group

When you first set up replication, you must choose a primary member. Choose the member that has the most up-to-date files that you want to replicate to all other members of the replication group, because the primary member's content is considered "authoritative" during initial replication. This means that during initial replication, the primary member's files will always win the conflict resolution that occurs when the receiving members have files that are older or newer than the associated files on the primary member.

The following concepts will help you better understand the initial replication process:

• Initial replication does not begin immediately. Configuration changes are not applied immediately to all members. The new configuration must be replicated to all domain controllers, and each member in the replication group must poll its closest domain controller to obtain the changes. The amount of time this takes depends on AD DS replication latency and the long polling interval (60 minutes) on each member. To poll immediately for configuration changes, open a command prompt window and then type the following command once for each member of the replication group: dfsrdiag.exe PollAD /Member:DOMAIN\Server1.
  
  
• Initial replication always occurs between the primary member and the receiving replication partners of the primary member. After a member has received all files from the primary member and completed building its database, initial replication is complete. The member will then replicate out any local files not already on the primary member. In this way, replication for a new replicated folder starts from the primary member and then progresses to the other members of the replication group.
  
  
• When receiving files from the primary member during initial replication, if a receiving member contains files that are not present on the primary member, those files are moved to their respective DfsrPrivate\PreExisting folder. If a file is identical to a file on the primary member, the file is not replicated. If the version of a file on the receiving member is different from the primary member’s version, the receiving member's version is moved to the Conflict and Deleted folder and remote differential compression (RDC) can be used to download only the changed blocks. To avoid conflicts, do not make changes to files in the replicated folder on non-primary members until initial replication completes.
  
  
• To determine whether files are identical on the primary member and receiving member, DFS Replication compares the files by using a hash algorithm. If the files are identical, only minimal metadata is transferred.
  
  
• After the initialization of the replicated folder, when all existing files in the replicated folder are added to the DFS Replication database, the primary member designation is removed. That member is then treated like any other member and its files are no longer considered authoritative over other members that have completed initial replication. Any member that has completed initial replication is considered authoritative over members that have not completed initial replication.