Years ago,I set a goal to become a full time author and write books that help others. Since then, I have authored or coauthored more than 30 books and regularly receive emails from readers sharing their successes with me after reading one of my books.
You can read those posts for more complete explanations. However, here is a synopsis of each.
Disaster recovery is a part of an overall business continuity plan. Often, an organization will use a business impact analysis to identify the critical systems and components. Security personnel then develop disaster recovery strategies and disaster recovery plans to ensure these systems will stay operational during and after a disaster.
Redundancy adds duplication to critical systems and provides fault tolerance. If a critical component has a fault, the duplication provided by the redundancy allows the service to continue without interruption. In other words, a system with fault tolerance can suffer a fault, but tolerate it and continue to operate.