AWS Disaster Recovery (DR)

1️⃣ Disaster Recovery (DR) Overview

Disaster Recovery (DR) is the process of restoring IT systems, applications, and data after an outage or disaster. In AWS, DR focuses on building highly available, fault-tolerant, and scalable architectures to minimize downtime and data loss.

Key objectives of DR:

  • Business Continuity: Keep services running or restore them quickly after a disaster.
  • Data Protection: Prevent data loss due to human error, cyberattacks, or natural disasters.
  • Cost Optimization: Choose DR strategies that balance recovery requirements with cost.

2️⃣ RPO and RTO

  • RPO (Recovery Point Objective):
    • Defines the maximum acceptable amount of data loss measured in time.
    • Example: RPO = 5 minutes → You can afford to lose only 5 minutes of data.
  • RTO (Recovery Time Objective):
    • Defines the maximum acceptable downtime after a disaster.
    • Example: RTO = 1 hour → Systems must be recovered within 1 hour.

✅ Goal: Lower RPO and RTO values → higher availability, but higher cost.

3️⃣ Disaster Recovery Strategies in AWS

AWS provides four common DR strategies:

Strategy RPO RTO Cost Description
Backup & Restore Hours Hours Low Data is backed up to AWS storage (S3, Glacier) and restored manually.
Pilot Light Minutes Hours Medium Minimal environment (critical services only) running, scaled up during disaster.
Warm Standby Minutes Minutes Higher Partially running environment with reduced capacity.
Hot/Active-Active Seconds Seconds Highest Fully replicated environment running across multiple regions.

4️⃣ DMS – Database Migration Service

AWS Database Migration Service (DMS) allows migrating databases to AWS securely with minimal downtime.

  • Supports: Homogeneous migrations (e.g., MySQL → MySQL) and heterogeneous migrations (e.g., Oracle → PostgreSQL).
  • Real-Time Replication: Continuous data replication while source DB remains operational.
  • Used with AWS Schema Conversion Tool (SCT) for schema and code conversion.

5️⃣ DMS Sources and Targets

  • Supported Sources:
    • On-premises databases (Oracle, SQL Server, MySQL, PostgreSQL, SAP ASE)
    • AWS RDS/Aurora
    • MongoDB, Amazon S3 (for data lakes)
  • Supported Targets:
    • AWS RDS (MySQL, PostgreSQL, MariaDB, Oracle, SQL Server)
    • Amazon Aurora
    • Amazon Redshift
    • Amazon S3
    • DynamoDB

6️⃣ AWS Schema Conversion Tool (SCT)

  • Converts database schema and SQL code from one engine to another (heterogeneous migrations).
  • Example: Oracle → PostgreSQL migration:
    • Converts tables, views, functions, stored procedures, triggers.
    • Generates a migration assessment report showing compatibility issues.

7️⃣ AWS DMS – Multi-AZ Deployment

  • Deploys replication instances across multiple Availability Zones (AZs).
  • Ensures high availability of migration tasks.
  • Automatic failover: If the primary instance fails, standby takes over without manual intervention.

8️⃣ RDS & Aurora MySQL Migrations

  • Use DMS for data replication and SCT for schema conversion if migrating from another DB engine.
  • Steps:
    • Create RDS or Aurora MySQL instance.
    • Set up DMS replication instance and tasks.
    • Perform full load + CDC (Change Data Capture) for near-zero downtime.
    • Test and cutover.

9️⃣ RDS & Aurora PostgreSQL Migrations

  • Similar process to MySQL migrations.
  • SCT often required when migrating from Oracle or SQL Server due to procedural language differences.
  • Use logical replication slots for PostgreSQL for continuous replication.

🔟 On-Premise Strategy with AWS

  • Hybrid approach: Keep primary workloads on-premises while replicating critical data to AWS for DR.
  • Use AWS Storage Gateway, Snowball, Direct Connect for data transfer.
  • Enable EC2 instances or VMware Cloud on AWS as a DR site.

11️⃣ AWS Backup

  • Centralized backup service to automate and manage backups across AWS services:
    • RDS
    • EBS volumes
    • DynamoDB
    • Amazon FSx
  • Supports cross-region backup, encryption, retention policies.

12️⃣ AWS Backup Vault Lock

  • WORM (Write-Once-Read-Many) protection for backup vaults.
  • Prevents accidental or malicious deletion of backups.
  • Helps meet compliance requirements like SEC 17a-4(f).

13️⃣ AWS Application Discovery Service

  • Helps plan migrations by identifying:
    • On-prem servers
    • Applications
    • Performance data
  • Collects metadata and utilization data for right-sizing AWS resources before migration.

14️⃣ AWS Application Migration Service (MGN)

  • Lift-and-shift (rehost) service for migrating physical, virtual, or cloud servers to AWS.
  • Automatically replicates source servers to AWS.
  • Minimizes downtime during cutover.

15️⃣ VMware Cloud on AWS

  • Allows running VMware workloads natively on AWS infrastructure.
  • Enables seamless migration from on-prem VMware environments to AWS.
  • Hybrid cloud option for DR, dev/test environments, or full migration.

16️⃣ Transferring Large Amounts of Data into AWS

  • Options:
    • AWS Snow Family: Snowcone, Snowball, Snowmobile for TB to PB-scale data transfer.
    • AWS Direct Connect: Dedicated high-speed network link to AWS.
    • S3 Transfer Acceleration: Speeds up uploads over long distances.
    • DataSync: Automates data transfer from on-prem to AWS storage.
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