highly critical application with no down time

HI experts,

1. I am looking data base solution for highly critical application. what type of HA/DR solution will suite for this.(always on, transactional , log shipping or mirroring). make sure all secondary nodes should be identical to production .

2. for any need to upgrade /patching /maintenance work,   production should not be able to down. No downtime 100%.

This HA/DR solution should be  able to manage online system 24*7*365

please let me know what kind of solution should be appropriate.

regards

Ashwan