We have an application that needs access to the database all the time to work properly and we are planning on deploying SQL Server 2012 AlwaysOn Availability Groups on Windows Server 2012.
We have two geographically separated data centers and we plan to keep one DB server in DC1 and the other in DC2.
All the information that I've seen shows a local synchronous copy and an asynchronous copy in another data center. I wanted to know if there is a way to configure the availability group with just two SQL servers which are separated geographically and can support automatic failover.
Best Answer
You can find here some design pattern for always on solutions http://blogs.msdn.com/b/sqlcat/archive/2013/11/20/sql-server-2012-alwayson-high-availability-and-disaster-recovery-design-patterns.aspx
just note that for automatic fail-over you may want to have synchronous commit so you dont loose data. also to have automatic fail-over you must have node majority to decide to do the fail-over. this mean you must have extra voter in the cluster. (eg' File Share Witness or another node)
this will prevent the problem known as Split Brain problem (https://en.wikipedia.org/wiki/Split-brain_(computing))
to summarize, this is very common need to have local automatic fail-over (because local LAN can serve synchronous mode) and another replica off-site with manual fail-over and asynchronous commit which can cause data loss when main site failed and not all data replicated yet to the another site.
I hope this have been informative for you. I will be glad to add information if you have any questions about that implementation.