Defining Disaster Recovery

By definition, recovery is the restoration or continuation of a technology infrastructure critical to an organization after a natural or human-induced disaster. Disaster recovery assumes that a major event has occurred, resulting in the loss of an entire site or a large section of infrastructure.

Disaster recovery is measured on recovery point objective and recovery time objective, two measurements that were discussed earlier in this chapter. Designing for disaster recovery differs from that of high-availability because the two goals, though they might seem relatively similar, are actually different. Designing for disaster recovery requires planning for redundant resources end to end, even across multiple sites. Additionally, disaster recovery planning involves defining a recovery playbook, which outlines exact steps for performing a recovery in the event of a disaster.

In its simplest form, disaster recovery for Lync implies deploying a secondary infrastructure that can support users in the event that the primary infrastructure is not available. However, the operational considerations for the recovery procedure often become much more complicated.

As the RPO and RTO objectives get closer to zero, the cost of the infrastructure and the operations will become much more expensive. This is why disaster recovery should be considered outside of the scope of high-availability and redundancy. High-availability should refer to the level of redundancy inside the pool of servers, or inside the Lync site. Disaster recovery should refer to how users will be provided services in the event of a total pool or total site loss.