Should I just create a VMDK of 10 TB and assign it to the virtual Fileserver ?
The maximu single VMDK size is still 2TB. You can create 5 or 6 of these and combine them within the fileserver though to give yourself a 10TB file system. Alternatively, use mount points and/or DFSto make it appear like you have a single large file system but break it up into smaller pieces so you can try to do backups or recoveries. You never want to corrupt a 10TB file system or you'll have a pretty lousy week. I saw a 6TB file system go corrupt once due to a bug in XFS. Ruined my Christmas (and that of a lot of other people) trying to recover the data.