DR for RDS

Here are the main strategies to implement Disaster Recovery (DR) for RDS databases, from simplest to most complex:

1. Backup and Restore:

• Simplest DR strategy

• Uses automated backups and snapshots

• Highest RPO/RTO

# Create manual snapshot
aws rds create-db-snapshot \
    --db-instance-identifier mydb \
    --db-snapshot-identifier mydb-snapshot

# Restore from snapshot
aws rds restore-db-instance-from-db-snapshot \
    --db-instance-identifier mydb-restored \
    --db-snapshot-identifier mydb-snapshot

1. Read Replicas:

• Cross-region read replica

• Can be promoted to master

• Lower RPO, moderate RTO

# Create cross-region read replica
aws rds create-db-instance-read-replica \
    --db-instance-identifier mydb-replica \
    --source-db-instance-identifier arn:aws:rds:us-east-1:123456789012:db:mydb \
    --region us-west-2

# Promote to master
aws rds promote-read-replica \
    --db-instance-identifier mydb-replica

1. Multi-AZ Deployment:

• Synchronous replication

• Automatic failover

• Zero RPO, low RTO

# Enable Multi-AZ
aws rds modify-db-instance \
    --db-instance-identifier mydb \
    --multi-az \
    --apply-immediately

1. Multi-Region Active-Passive:

• Primary region active

• Secondary region with read replica

• Can be promoted during DR Steps:

1. Create cross-region read replica

2. Set up monitoring

3. Create failover procedure

4. Test regularly

5. Multi-Region Active-Active:

• Both regions active

• Uses Route 53 for routing

• Most complex but lowest downtime Components needed:

• Cross-region read replicas

• Route 53 health checks

• Application logic for write distribution

Key Considerations:

1. RPO (Recovery Point Objective):

• Backup/Restore: Hours

• Read Replica: Minutes

• Multi-AZ: Seconds

• Multi-Region: Minutes to seconds

1. RTO (Recovery Time Objective):

• Backup/Restore: Hours

• Read Replica: Minutes

• Multi-AZ: Minutes

• Multi-Region: Minutes to seconds

1. Cost Implications:

• Backup/Restore: Lowest cost

• Read Replica: Moderate cost

• Multi-AZ: Higher cost

• Multi-Region: Highest cost

1. Best Practices:

• Document DR procedures

• Regular testing

• Automated failover when possible

• Monitor replication lag

• Consider automated DR tools

• Maintain up-to-date DNS records

• Regular backup validation

1. Additional Considerations:

• VPC peering/Transit Gateway setup

• Security group configurations

• IAM roles and permissions

• SSL/TLS certificates

• Database parameter groups

• Option groups

• Monitoring and alerting setup

• Network latency between regions