Disaster Recovery versus High Availability
Note the essential definitions for the discussion here. A disaster refers to a large-scale event that impacts a broad geographical area. In AWS terms, a disaster may impair an Availability Zone (AZ), multiple AZs, an entire AWS Region, or, worse, several Regions.
Disaster recovery (DR) is the process that tackles both the prevention of a disaster and the recovery from a disaster.
High availability (HA) addresses how a workload can keep functioning even though some of its components are impacted by a failure.
How do the two compare with each other? Simply put, HA deals with local failures while DR deals with large-scale failures, so they complete each other.
That said, designing for HA on AWS often brings some form of protection for DR at the same time. Why is that? That is because AWS reliability best practices (see Chapter 6, Meeting Reliability Requirements, for more details) recommend measures that also provide some level of...
