It is highly recommended to implement at least two logical sites for large implementations of the business service's application platform. As we understand that high availability of business services is critical for any organization, it is recommended that you design two physical sites that provide you with built-in backup and recovery of the mission-critical business service's application platform.
You are at least required to implement an off-site backup solution for one physical site design and deployment. On other hand, if your implementation is with two sites, you may be able to live on an on-site disk-based backup solution as these sites could provide the backup for each other. Some of the implementations, irrespective of the number of physical sites, may still require implementing an off-site backup solution due to industry compliance and business policies.
As a minimum, we need to create a backup and recovery for databases, logfiles from all the servers...