Design infrastructure solutions · Topic 6 of 10
Migration Planning and the Cloud Adoption Framework
AZ-305 migration planning: the Cloud Adoption Framework phases, assessing servers and apps with Azure Migrate, the five Rs, landing zones and choosing IaaS or PaaS.
- 4 min
- CAF phases: strategy, plan, ready, migrate, innovate, govern, manage. Ready uses Azure landing zones.
- Azure Migrate discovers with an appliance, assesses readiness, sizing and cost, and offers dependency analysis and a business case.
- The five Rs: rehost, refactor, rearchitect, rebuild, replace.
What it is
A migration is a project, not just a data copy. Microsoft's Cloud Adoption Framework (CAF) provides a structured approach, from strategy to ongoing management. Within it, the architect evaluates the current estate, decides how each workload moves (the five Rs), prepares a landing zone and chooses between IaaS and PaaS targets.
How it works
Cloud Adoption Framework phases
| Phase | Purpose |
|---|---|
| Strategy | Business motivations and outcomes |
| Plan | Digital estate, skills, adoption plan |
| Ready | Prepare the environment: Azure landing zones |
| Migrate | Assess, deploy and release workloads |
| Innovate | Build new cloud native solutions |
| Govern | Policy, cost and security governance |
| Manage | Operations baseline and ongoing management |
An Azure landing zone is a scalable, secure environment with identity, networking, governance and management ready before workloads arrive. Use the landing zone accelerators and the management group design (platform and landing zones) described earlier.
Evaluating on premises estate
Assessment answers: what exists, what depends on what, is it ready, what will it cost and what size it needs.
| Tool | Role |
|---|---|
| Azure Migrate: Discovery and assessment | A lightweight appliance discovers servers (VMware, Hyper-V, physical, AWS, GCP) and collects configuration and performance data. Produces readiness, sizing and cost assessments as point in time snapshots. The core service is free |
| Dependency analysis | Maps connections between servers, so you migrate related workloads together |
| Azure Migrate business case | Builds a financial case, including TCO and savings |
| Data Migration Assistant and Azure Migrate database assessments | Check SQL Server compatibility with Azure SQL targets |
| Azure App Service migration assistant | Assesses web apps |
| Azure Total Cost of Ownership tools and Azure pricing calculator | Cost modelling |
Use performance based sizing (right sizing from observed utilisation) rather than as is sizing to avoid overspending. Evaluate applications, not only servers: language and framework versions, licensing, data residency, latency, compliance and dependencies on on premises systems.
The five Rs
| Strategy | Meaning | Effort |
|---|---|---|
| Rehost | Lift and shift to IaaS with no change | Lowest |
| Refactor | Minor changes to use PaaS (for example move to App Service or Azure SQL) | Low to medium |
| Rearchitect | Redesign for cloud native (microservices, containers) | High |
| Rebuild | Rewrite on cloud native services | Highest |
| Replace | Swap for a SaaS product | Varies |
Choose the strategy per workload. Rehost is fastest and good for deadline driven moves, such as a datacenter exit. Refactor and rearchitect deliver more cloud benefits. Retire unused apps and retain those that cannot move. Use Azure Arc for resources that stay.
Choosing IaaS or PaaS
| Prefer | When |
|---|---|
| IaaS (VMs) | Quick lift and shift, OS level control, unsupported software, strict compatibility |
| PaaS | Less management, built in scaling and availability, and the app can use supported runtimes |
| Containers | Existing containers or microservices, or apps being modernised |
| SaaS | A commodity capability with an acceptable product |
Typical PaaS targets: web apps to App Service, SQL Server to SQL Database or Managed Instance, file servers to Azure Files, identity to Entra ID. A good migration plan often rehosts first, then modernises.
Planning considerations
- Sequence in waves with dependencies together, and start with low risk workloads.
- Network: connectivity (VPN or ExpressRoute), IP address planning, DNS.
- Identity and governance ready in the landing zone.
- Data transfer method and window (next page).
- Cutover and rollback plan, with testing and a validated rollback.
- Licensing: Azure Hybrid Benefit and reserved instances.
- Skills and operating model (cloud centre of excellence).
Choosing quickly
| Requirement | Answer |
|---|---|
| Discover servers and their dependencies before migrating | Azure Migrate with the appliance and dependency analysis |
| Move quickly with minimal changes before a datacenter lease ends | Rehost |
| Reduce management of a web app with small code changes | Refactor to App Service |
| Prepare identity, network and policy before moving | An Azure landing zone |
| Estimate cost and savings for approval | An Azure Migrate business case |
A worked scenario
A retailer must leave its datacenter in 12 months. The architect runs Azure Migrate discovery across 600 servers with dependency analysis, groups them into waves, and builds a business case. Most servers are rehosted into a prepared landing zone, the intranet web apps are refactored to App Service, and the SQL Servers move to Managed Instance. A retired inventory app is decommissioned.
What to remember for the exam
- CAF phases: strategy, plan, ready, migrate, innovate, govern, manage. Ready uses Azure landing zones.
- Azure Migrate discovers with an appliance, assesses readiness, sizing and cost, and offers dependency analysis and a business case.
- The five Rs: rehost, refactor, rearchitect, rebuild, replace.
- Performance based sizing avoids overspending.
- Rehost first and modernise later is a common pragmatic path.
"Minimal change, fastest" is rehost. "Reduce management, small changes" is refactor to PaaS.
How the exam asks about this
- "Discover servers and map their dependencies." Azure Migrate with dependency analysis.
- "Move with no code changes before a deadline." Rehost.
- "Environment prepared with identity, network and policy before migration." An Azure landing zone.
- "Estimate savings to justify the project." The Azure Migrate business case.
Common mistakes
Migrating without assessing dependencies. Apps break when split.
As is sizing. Pay for unused capacity.
Rearchitecting everything first. Delivery slows.
Skipping the landing zone.
Check yourself
What does the Azure Migrate appliance do?
Discovers servers and collects configuration and performance data for assessment.
Which R means lift and shift?
Rehost.
What should exist before workloads arrive?
An Azure landing zone.
Topic 6 of 10 in Design infrastructure solutions
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