Dan Guzman - Not the MVP (8/20/2010)
So....Why not just fail over to the secondary full time, so that you can upgrade the primary offline. If all goes well, fail back to the primary, if not, the secondary keeps on running until the issues are resolved? No down time at all.
You would have to break mirroring or log shipping in order to have both primary and secondary databases online at the same time. How would you reconcile the difference between the primary which has the code upgrade applied and the secondary which has had user transactions running against it?