At the SharePoint Conference in Anaheim was demoed using SQL Server “Denali” Always On to fail-over a 14.4 TB SharePoint content database to a secondary database server in 45 seconds. Very impressive, and you are able to get more information here including seeing the video of the event.
The 10 minute full farm failover keynote demo is here:
Note. This is a SQL failover, not a physical infrastructure failover – so to have a full DR for the entire SharePoint environment so say fail to another datacenter you would need to factor in failing over the Web front ends and associated pieces.
There’s more though!
Paul Andrew has also published the report covering the Very Large Scale Document Archive Test Report
with all the details on the scalability lab results here: http://blogs.msdn.com/b/pandrew/archive/2011/10/03/sharepoint-scalability-report-and-the-sharepoint-conference-2011-keynote-demo.aspx