Backing up data is never a bad idea since it can provide handy insurance against accidental data loss. The DFS Replication service is designed to interoperate with the backup/restore interfaces exposed by the Windows Volume Shadow Copy Service (VSS).
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Read the complete post at http://blogs.technet.com/filecab/archive/2008/06/18/backup-restore-of-dfsr-replicated-data-part-1-introduction.aspx