I have been doing some research on running virtual SBS 2008/2011 Premium (SBS + SQL ) for small clients and still have backups to tape – Single server solution. SCSI tape device pass-through is known to cause a few issues on VMWare.
Traditionally you cannot install backup exec for SBS on a standard windows server. Symantec have fixed this issue starting with Backupexec 2010 R2 as long as you have SBS on a guest VM. You can install backupexec on the HyperV parent partition (Windows 2008 R2 Server) and configure backups to tape.
http://technet.microsoft.com/en-us/library/dd239200%28WS.10%29.aspx
http://www.symantec.com/business/support/index?page=content&id=TECH125965
