Migrating SYSVOL to DFS-R

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Once all the domain controllers in a domain are running Windows Server 2008 and above, you can change the SYSVOL replica set to use DFS-R (as opposed to FRS). The key benefits of migrating to DFS-R are

  1. Self healing functionality (e.g. journal wraps)
  2. Improved RODC support
  3. Efficient replication

Note that the https://blogs.technet.com/askds/archive/2009/05/01/sysvol-migration-from-frs-to-dfsr-whitepaper-released.aspx provides details of the process to migrate to DFS-R. The key points I would recommend anyone follow in any environment migrating SYSVOL to DFS-R are

  1. Ensure FRS based SYSVOL is healthy (https://blogs.technet.com/askds/archive/2008/05/22/verifying-file-replication-during-the-windows-server-2008-dfsr-sysvol-migration-down-and-dirty-style.aspx)
  2. Run dfsrmig.exe to change globalstate in gradual steps. Don’t go to eliminated at once.
  3. Stay in redirected for a while ( a few days at least) and ensure DFS-R is working. The health reports with backlog details are available from DFS management console. Note that the DFS management console is not installed by default on a DC.
  4. Once DFS-R based SYSVOL is confirmed as converging from step 3, go to eliminated stage. This will remove FRS replica set.

Regular backups of the contents of SYSVOL is essential throughout the migration. This helps if the replica set needs to be recreated from scratch for some unfortunate reason.

Also note that even while in redirected mode, the FRS replica sets health must be monitored. Note that any new DC initialises SYSVOL first by creating a FRS based replica set and then by migrating it to DFS-R. If FRS is broken, this will prevent creating the temporary FRS replica required in order to go to DFS-R. Therefore, I recommend eliminating the FRS replica set as soon as possible.

 

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