Skip to main content
Future Solutions Architects — this lesson gives a concise, practical overview of reliability for storage services on AWS and what to expect on the associate-level exam. Most of the heavy lifting for reliability is handled by AWS-managed storage services, which is why architects rely on them. Still, you need to design systems that handle redundancy, failure domains, and recovery strategies to meet availability and recovery objectives.
AWS-managed storage services provide high durability and availability by default, but architects must design for redundancy, failure isolation, and recovery to meet business SLAs and disaster-recovery goals.

​
What this lesson covers

  • Core reliability principles for storage on AWS
  • How storage and compute resilience map to each other
  • What the exam expects you to know
  • Practical design actions for S3, EBS, and managed databases

​
Key concepts

  • AWS storage services (for example, Amazon S3) store multiple redundant copies of your data across devices and infrastructure for very high durability. S3’s durability is commonly described as “11 nines” (99.999999999%) because of this redundancy and internal replication.
  • Architecturally, reliability is achieved through redundancy and isolation — distribute data or instances across distinct failure domains (for example, multiple Availability Zones or Regions).
  • The same resilience patterns apply across layers: run multiple instances, use Auto Scaling and load balancers, and design stateless services so individual instance failures don’t cause service outages.

​
Storage vs. Compute — how the concepts map

  • Storage: durable systems keep redundant copies of data so losing a device or facility does not lose data.
  • Compute: running multiple instances (e.g., three application nodes behind a load balancer) tolerates individual instance failures — the remaining instances continue serving traffic.
  • Common resilience patterns across layers: redundancy, isolation of failure domains, rapid failover or recovery.

​
Durability vs. Availability

​
What to expect on the exam and in architecture design

  • Differentiate when to use AWS-managed storage (built-in redundancy) versus when you need additional replication, snapshots, or backups.
  • Understand failure domains: Availability Zones (AZs) and Regions.
    • Cross-AZ replication improves availability and fault isolation.
    • Cross-Region replication supports disaster recovery and geographic resilience.
  • Know common AWS features for reliability: S3 versioning/CRR, EBS snapshots, Multi-AZ RDS and read replicas, and lifecycle policies for long-term retention.
Exam tips: focus on which AWS features provide durability versus which address availability and recovery. Be ready to recommend cross-AZ for availability and cross-Region for disaster recovery.

​
Example design considerations and practical actions

​
Practical checklist

  • Identify your RPO (Recovery Point Objective) and RTO (Recovery Time Objective).
  • Choose replication strategy based on RPO/RTO: cross-AZ for high availability, cross-Region for DR.
  • Implement automated backups and lifecycle policies.
  • Design stateless application tiers and store state in durable, replicated services (S3, managed databases, DynamoDB).
  • Test failover and recovery procedures regularly.

​
Quick examples and reminders

  • S3: enable Versioning and consider CRR when you need geographic redundancy. Use lifecycle rules to transition older objects to cheaper storage classes.
  • EBS: use snapshots for backups; snapshots are stored in S3 and can be copied to other Regions for recovery.
  • Databases: prefer managed Multi-AZ deployments for high availability; use read replicas and cross-Region replicas for scaling and DR.
Final note These resiliency principles apply across compute and storage: increase redundancy, distribute across AZs/Regions, and design for rapid recovery. Storage services provide many durability guarantees by default, but architectural decisions about replication, backups, and failover are what make a system truly reliable end-to-end. — Michael Forrester I appreciate you reading this lesson.

Watch Video