AWS Migration Strategy Guide: Determining the Optimal Migration Approach

This guide covers the strategic framework for migrating on-premises workloads to AWS, specifically aligned with Domain 4 (Accelerate Workload Migration and Modernization) of the AWS Certified Solutions Architect - Professional (SAP-C02) exam.

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Learning Objectives

After studying this guide, you should be able to:

• Categorize applications using the 7 Rs of Migration.
• Evaluate total cost of ownership (TCO) for cloud migration.
• Select appropriate data migration tools (Snow Family, DataSync, S3 Transfer Acceleration) based on volume and bandwidth.
• Differentiate between Application Migration Service (MGN) and Database Migration Service (DMS).
• Design a Landing Zone using AWS Control Tower for secure, governed migration targets.

Key Terms & Glossary

• 7 Rs: The set of strategies for migrating applications to the cloud (Retire, Retain, Relocate, Rehost, Replatform, Repurchase, Refactor).
• TCO (Total Cost of Ownership): A financial estimate intended to help buyers determine the direct and indirect costs of a product or system.
• Landing Zone: A well-architected, multi-account AWS environment that is a starting point from which you can deploy workloads and applications.
• Migration Wave: A group of applications or workloads scheduled to be migrated together based on shared dependencies or business priority.
• CMDB (Configuration Management Database): A repository that acts as a data warehouse, storing information about IT assets and their relationships.

The "Big Idea"

Migration to AWS is not a "one-size-fits-all" event but a strategic process of aligning business requirements with technical constraints. The "Optimal Approach" is found by balancing the speed of migration against the degree of modernization. Organizations must move from an "Assess" phase (readiness) to a "Mobilize" phase (planning/foundations) before executing the actual migration of workloads.

Formula / Concept Box

Migration Feasibility Calculation

While not a mathematical formula, the feasibility of a migration strategy is often judged by:

Hierarchical Outline

1. Discovery & Assessment
   • AWS Application Discovery Service: Inventorying assets and mapping dependencies.
   • Migration Hub: Centralized tracking for migration progress.
2. The 7 Rs Strategy Selection
   • Retire: Removing obsolete apps.
   • Retain: Keeping apps on-prem (compliance/latency).
   • Relocate: Hypervisor-level transfer (VMware Cloud on AWS).
   • Rehost: Lift-and-shift using AWS Application Migration Service (MGN).
   • Replatform: Lift-and-reshape (e.g., moving to Managed RDS).
   • Repurchase: Moving to SaaS (e.g., Salesforce, Workday).
   • Refactor: Rearchitecting for microservices or Serverless.
3. Data Transfer Mechanisms
   • AWS Snow Family: Offline transfer for PB-scale data.
   • AWS DataSync: Automated online transfer for EFS/S3.
   • AWS Transfer Family: Managed SFTP/FTPS/FTP.
4. Foundation & Governance
   • AWS Control Tower: Setting up the multi-account Landing Zone.
   • AWS Organizations: Managing billing and SCPs (Service Control Policies).

Visual Anchors

Migration Journey Flowchart

Migration Effort vs. Value Matrix

\begin{tikzpicture}[scale=0.8] \draw[thick,->] (0,0) -- (8,0) node[anchor=north] {Business Value / Cloud Benefit}; \draw[thick,->] (0,0) -- (0,8) node[anchor=east, rotate=90] {Migration Effort};

\end{tikzpicture}

Definition-Example Pairs

• Rehosting (Lift & Shift): Moving an application as-is to EC2 instances.
  • Example: Moving an on-premises Windows Server 2016 running a custom accounting app to an EC2 m5.large instance using AWS MGN.
• Replatforming (Lift & Reshape): Making minor changes to take advantage of cloud benefits without changing core architecture.
  • Example: Migrating a self-managed Oracle database on-premises to Amazon RDS for Oracle to automate patching.
• Refactoring: Reimagining the application using cloud-native features.
  • Example: Breaking a monolithic Java application into AWS Lambda functions and using Amazon DynamoDB for storage.

Worked Examples

Scenario 1: Data Migration under Constraints

Problem: A company needs to migrate 500 TB of data to AWS S3. Their available internet bandwidth is a dedicated 100 Mbps, but they must complete the transfer within 2 weeks.

Analysis:

• 500 TB @ 100 Mbps (assuming 80% utilization) = $\frac{500 \times 1024 \times 1024 \times 8}{100 \times 0.8 \times 3600 \times 24} \approx 600$ days.
• This exceeds the 14-day window significantly.

Solution: Use AWS Snowball Edge. Request 7-8 Snowball Edge Storage Optimized devices (80TB usable each). Ship them to AWS. Total time: ~2-3 days shipping + 2 days loading + 2 days return shipping/upload = ~7-10 days.

Checkpoint Questions

1. Which migration strategy involves moving virtual machines at the hypervisor level to a managed service? (Answer: Relocate)
2. What is the primary tool used to convert database schemas from proprietary (e.g., SQL Server) to open-source (e.g., Aurora PostgreSQL)? (Answer: AWS Schema Conversion Tool / SCT)
3. True or False: AWS DataSync is an offline data transfer tool. (Answer: False - it is online over the network/Direct Connect)
4. What phase of migration involves building the landing zone and creating a detailed business case? (Answer: Mobilize Phase)

Muddy Points & Cross-Refs

• Rehost vs. Relocate: Students often confuse these. Remember: Relocate requires a common hypervisor (specifically VMware Cloud on AWS), whereas Rehost uses agents or snapshots to move to EC2 regardless of the source hypervisor.
• S3 Transfer Acceleration vs. DataSync: Use Transfer Acceleration for one-off uploads from globally distributed clients; use DataSync for recurring, large-scale data migrations between storage systems.

Comparison Tables

Migration Tooling Matrix