Multi-AZ Backup Architectures
Why Multi-AZ Backup Architectures Matter
Multi-AZ backup architectures are fundamental to achieving high availability and disaster recovery in AWS. They protect your data and applications against infrastructure failures, natural disasters, and other disruptions that could affect a single Availability Zone. For the AWS Solutions Architect Professional exam, understanding these architectures is critical as they form the backbone of resilient solution design.
What Are Multi-AZ Backup Architectures?
Multi-AZ backup architectures distribute data copies and backup resources across multiple Availability Zones within an AWS Region. An Availability Zone consists of one or more discrete data centers with redundant power, networking, and connectivity. By spanning multiple AZs, you ensure that a failure in one zone does not result in data loss or extended downtime.
Key Components and Services
Amazon RDS Multi-AZ Deployments: RDS automatically provisions and maintains a synchronous standby replica in a different AZ. Failover is automatic and typically completes within 60-120 seconds.
Amazon Aurora: Stores six copies of your data across three AZs automatically. Aurora can lose up to two copies of data and still maintain write availability, or three copies and maintain read availability.
Amazon EBS Snapshots: Snapshots are stored redundantly across multiple AZs within a region in Amazon S3. This provides 99.999999999% durability.
AWS Backup: A centralized service that automates backup across AWS services including EBS, RDS, DynamoDB, EFS, and Storage Gateway across multiple AZs.
Amazon S3: Automatically stores data redundantly across a minimum of three AZs, providing built-in resilience.
Amazon EFS: Stores data redundantly across multiple AZs, providing high availability for file storage workloads.
How Multi-AZ Backup Architectures Work
1. Synchronous Replication: Services like RDS Multi-AZ use synchronous replication to ensure data consistency. Every write to the primary is replicated to the standby before acknowledgment.
2. Asynchronous Backup: EBS snapshots and AWS Backup perform point-in-time backups that are stored across multiple AZs for durability.
3. Automatic Failover: When a primary resource fails, the system automatically promotes a standby or redirects traffic to healthy resources in another AZ.
4. Recovery Point Objectives (RPO): Multi-AZ synchronous replication typically provides near-zero RPO, while snapshot-based backups have RPO equal to the time since the last backup.
5. Recovery Time Objectives (RTO): Automated failover mechanisms minimize RTO, often achieving recovery in minutes rather than hours.
Architecture Patterns
Active-Passive: Primary resources operate in one AZ with standby resources in another AZ ready for failover.
Active-Active: Resources in multiple AZs actively serve traffic, with load balancing distributing requests. If one AZ fails, the remaining AZs handle the load.
Pilot Light: Minimal backup infrastructure runs in secondary AZs and can be scaled up rapidly during a disaster.
Exam Tips: Answering Questions on Multi-AZ Backup Architectures
1. Identify the RPO and RTO requirements: Questions often specify these metrics. Synchronous replication suits near-zero RPO needs, while periodic snapshots work for less stringent requirements.
2. Understand service-specific Multi-AZ behavior: Know that RDS Multi-AZ uses synchronous standby replication, Aurora uses distributed storage, and DynamoDB global tables replicate across regions.
3. Cost considerations: Multi-AZ deployments typically double infrastructure costs. If a question emphasizes cost optimization with relaxed availability requirements, consider single-AZ with cross-region backups.
4. Differentiate Multi-AZ from Multi-Region: Multi-AZ protects against AZ failures within a region. For regional disaster protection, Multi-Region architectures are necessary.
5. Look for keywords: Terms like high availability, automatic failover, synchronous replication, and durability typically point toward Multi-AZ solutions.
6. Backup retention and compliance: When questions mention compliance or long-term retention, consider AWS Backup with lifecycle policies and cross-region copy rules.
7. Encryption requirements: Remember that backups inherit encryption settings from source resources. For compliance scenarios, ensure encryption is addressed in your answer.
8. Application-consistent backups: For databases and applications requiring consistent state, look for answers involving VSS-enabled snapshots or native database backup tools integrated with AWS Backup.