It is safe. This is a procedure I used when moving from the Vail beta to full WHS 2011 which should be applicable to your situation:
- In Vail, moved all shared folders via the Dashboard to my main 2TB data drive
- Shut down Vail and removed connections to 2TB drive and did a fresh WHS2011 install on the 500GB boot disk on which Server Folders were created.
- Shut down server and reconnect 2TB drive. Booted and renamed all Server Folders on 2TB drive as NameOld (e.g. MusicOld)
- Ran the Move Folder wizard from the Dashboard to move Shared folders from D: to E: (2TB drive).
- Logged in locally and moved files from MusicOld to Music (both on same 2TB disk) and deleted the NameOld folders.
This worked for all my data and took no time at all as there was no copying from disk to disk.
Phil P.S. If you find my comment helpful or if it answers your question, please mark it as such.