RD and Michael,
It is a copy (sometimes) in 10.1. Are you using 10.1 for ArcGIS Server? I use SDE and FGDB data for my map services and performing a schema change require an exclusive lock on the data and can not be a shared lock. So when I want to add a field to a FC in one of my GDBs that is included in a Map Service I always have to stop that map service, make the change, save the mxd, overwrite the MSD, restart the map service, clear the REST cache.