Multi-AZ Deployments

High Availability & Disaster Recovery

Multi-AZ Concepts

Availability Zones

Isolated data centers within a region

Fault Isolation

Failures in one AZ don't affect others

Low Latency

High-speed connectivity between AZs

Redundancy

Deploy across multiple AZs for resilience

RDS Multi-AZ

Synchronous Replication

Data replicated to standby in real-time

Automatic Failover

Failover within 60-120 seconds

No Performance Impact

Standby not accessible for reads

Maintenance Benefits

Zero-downtime maintenance

Multi-AZ Architecture Patterns

Web Tier

Load balancer across AZs

  • • ALB/NLB in multiple AZs
  • • Auto Scaling Groups
  • • Cross-zone load balancing

Application Tier

Stateless application servers

  • • EC2 instances in multiple AZs
  • • Session state in ElastiCache
  • • Auto Scaling for resilience

Database Tier

Multi-AZ RDS deployment

  • • Primary in one AZ
  • • Standby in another AZ
  • • Automatic failover

Failover Mechanisms

DNS Failover

Route 53 health checks and failover

ELB Health Checks

Automatic traffic rerouting

Auto Scaling

Replace failed instances automatically

RDS Failover

Automatic database failover

Disaster Recovery

RTO (Recovery Time)

Time to restore service after failure

RPO (Recovery Point)

Maximum acceptable data loss

Cross-Region

Replicate to different AWS regions

Backup Strategies

Automated backups and snapshots

Multi-AZ Deployments Exam Tips

  • • Multi-AZ is for high availability, not performance - standby replicas are not readable
  • • RDS Multi-AZ provides automatic failover within 60-120 seconds
  • • ELB automatically distributes traffic across healthy instances in multiple AZs
  • • Auto Scaling Groups should span multiple AZs for maximum availability
  • • Use Route 53 health checks for DNS-based failover between regions
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