GuideTechnology
14 min read
High Availability and Disaster Recovery: Redundancy, Failover, RPO, RTO and Multi-Region
How systems survive failures of servers, availability zones and whole regions, and recover from data disasters. Covers failure domains, redundancy and failover, availability arithmetic with correlated failures, RPO and RTO, the four disaster-recovery strategies from backup-and-restore to active-active, multi-region write strategies, backups that actually restore, and safe deployments.