Recommended plan for 0min RTO and RPO I have a Windows Server 2008R2 Server, running SQL Server 2008R2 SP2. The server currently only does a full backup once daily. The server's operational hours are between 8am and 5pm. The server's new RTO is 0mins and it's RPO is 0mins during operational hours. What is the best option in achieving this? I have currently thought of an AlwaysOn Availability Cluster. As for backups I have thought of Transactional Log backups every 15mins, Differential backups every 2 hours, and keeping the Full backup every day. Is my plan sufficient?

Also with an AlwaysOn Availability Cluster, do I just need 1 additional server to be a replica or do I really need a Primary Replica and Secondary Replica? (still very confused about AlwaysOn...)

If I implement AlwaysOn, do I really need to backup each server?

If I implement AlwaysOn, do I really need to use a SAN?

Are there any performance impacts doing backups doing business hours?
You could implement database mirroring.  Synchronous database mirroring provides a mechanism to ensure all writes on the primary mirrored databases are sent to the secondary machine prior to being committed on the primary.  This is designed to provide an RPO as close to zero as practically possible.

In the event the primary goes down for any reason, the secondary mirror will become the primary and resume serving clients once it completes the recovery process for the database in question.  Recovery can take a very short amount of time assuming you ensure the redo queue is being processed reliably.