The purpose of disaster recovery is not to directly save cost, but to save opportunity cost in times of disaster — protecting the business from potential losses and irrecoverable damage.
In our experience, when we discuss DR, clients ask us a similar set of questions: What is the right DR? Should I build a DR for only critical applications? When should I switch to the DR? Disaster Recovery is at a site level. It is appropriate for cases when the whole of primary site is down, either due to natural or man-made calamity and would require days if not weeks to recover. It is the minimum readiness from IT in an alternate site for business to continue without major impact to end the customer.
The recovery time objective (RTO) and the recovery point objective (RPO) are two very specific parameters closely associated with recovery.
The RTO is the duration within which the application must be restored to ensure uninterrupted business continuity.
While RPO dictates the allowable data loss — how much data can you afford to lose? It is useful for determining how often to perform data backups.