Are the Classical Disaster Recovery Tiers Still Applicable Today?

As disaster recovery plans (DRPs) for IT systems have been improving over the past decades, some metrics became widely accepted such as recovery time objective (RTO) and recovery point objective (RPO). However, disaster recovery plans and solutions vary in their design, sophistication and their required RTO/RTO. Therefore, a need to categorize disaster recovery plans into tiers has become necessary. Fortunately, a number of classifications exist but sometimes they are not fully explained, so, independent researchers may find the classification confusing or inappropriate for the current state of technology with significant overlap among tiers. Moreover, advances in communication and technology and the introduction of disaster recovery as a service (DRaaS) by several cloud service providers (CSPs) has reshaped the area of disaster recovery and development of DRPs. Therefore, one can argue that the old classification of 7-tiers of DRPs is obsolete and a new classification is needed. Here, we try to survey these classifications, understand the common grounds and the differences and try to suggest some improvements to gap them.