We have SBS 2011 standard sp2 and we have configured AD, SQL 2008 R2 and file server in SBS 2011.
We need to add a new domain with windows server 2012 which will act as primary.
Further more we need to configure SQL failover as below
SBS: 2011 standard with SQL 2008 Express and
Windows server 2012 with SQL 2008 R2.
and file server failover as belwo
SBS: 2011 File server and
Windows server 2012 with file server role