What to expect during initial replication
Updated: August 22, 2005
Applies To: Windows Server 2003 R2
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 replicated to all other members of the replication group, because the primary member's content is considered "authoritative." 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 compared to the same files on the primary member.
The following concepts will help you better understand the initial replication process:
Initial replication does not begin immediately. The topology and DFS Replication settings must be replicated to all domain controllers, and each member in the replication group must poll its closest domain controller to obtain these settings. The amount of time this takes depends on Active Directory replication latency and the long polling interval (60 minutes) on each member.
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, then that member will replicate files to its receiving partners as well. In this way, replication for a new replicated folder starts from the primary member and then progresses out to the other members of the replication group.
When receiving files from the primary member during initial replication, the receiving members that contain files that are not present on the primary member move those files 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 determine whether files are identical on the primary member and receiving member, DFS Replication compares the files using a hash algorithm. If the files are identical, only minimal metadata is transferred.
After the initialization of the replicated folder, the "primary member" designation is removed. (Initialization takes place after all files that exist before DFS Replication picks up the configuration are added to the DFS Replication database.) 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.