DR_HA

Disaster Recovery (DR)

• Strategic and methodical approach to restoring systems or critical parts of them, after a major failure event
• Major Failure Events include:
  • Regional Outages
  • Corrupted environment due to malicious activity
  • Severe infrastructure failures
  • Natural disasters or geopolitical events causing extended service unavailability
• Recovery Time Objective (RTO)
  • How quickly a system must be restored after a disruption
• Recovery Point Objective (RPO)
  • How much data loss is acceptable and reflects how frequently data must be backed up
• https://learn.microsoft.com/en-us/azure/well-architected/design-guides/disaster-recovery

DR Strategies

• Active-Active (Hot Standby)
  • Two or more environments fully operational and serving live traffic simultaneously across multiple regions
  • If one environment fails, others continue handling the load with zero or near-zero disruption.
• Active-Passive (Warm Standby)
  • Partially provisioned environment running minimal services that can scale up quickly during failures
• Active-Passive (Cold Standby)
  • Environment that isn’t running and requires provisioning and data restoration when activated. Lowest cost, longest recovery time.

Failover and Failback

• Failover
  • Process of shifting workloads from primary to standby environment during a disaster
• Failback
  • Process of returning workloads to the original primary environment after incident resolution
• https://learn.microsoft.com/en-us/azure/reliability/concept-failover-failback

High Availability (HA)

• Designing solution to be resilient to day-to-day issues and to meet the business needs for Availability
• HA Design Elements
  • Fault tolerance
  • Redundancy
  • Scalability and elasticity
  • Automated testing using Chaos engineering
  • Monitoring and alerting
• https://learn.microsoft.com/en-us/azure/reliability/concept-business-continuity-high-availability-disaster-recovery