Cloud migration isn't a simple "lift and shift" exercise. It's a strategic transformation that requires careful planning, application assessment, and execution. Rushed migrations result in cloud environments that cost more than on-premise while delivering fewer benefits.
The 7 Rs of Migration
Not every application should be migrated the same way. The 7 Rs framework helps categorise workloads:
1. Rehost (Lift and Shift)
Move applications as-is to cloud infrastructure. Fastest approach but captures fewest cloud benefits. Good for quick wins, applications nearing end of life, or as a stepping stone.
2. Replatform (Lift, Tinker, and Shift)
Make minimal changes to take advantage of some cloud capabilities. Move database to managed service. Containerise application. Balance of speed and benefit.
3. Refactor (Re-architect)
Redesign application to be cloud-native. Microservices, serverless, managed services. Highest benefit but highest effort. Reserve for strategic applications.
4. Repurchase
Replace with SaaS alternative. Move from on-premise CRM to Salesforce. From local email to Microsoft 365. Often the best option for commodity applications.
5. Retire
Identify and decommission applications that are no longer needed. Migration is an opportunity to reduce the application portfolio.
6. Retain
Keep on-premise for now. Regulatory requirements, technical constraints, or pending retirement. Plan for future migration.
7. Relocate
Move entire infrastructure to cloud - VMware on AWS, Azure VMware Solution. Preserves existing architecture while moving to cloud hardware.
Migration Assessment
Discovery
Inventory all applications, servers, databases, and dependencies. Many organisations don't have accurate documentation. Use automated discovery tools.
Application Analysis
For each application, assess:
- Business criticality
- Technical complexity
- Dependencies and integrations
- Performance requirements
- Compliance and data residency requirements
- Licensing implications
Migration Strategy Assignment
Based on analysis, assign a migration strategy (one of the 7 Rs) to each workload. Consider both technical and business factors.
Assessment Questions
- Is there a SaaS alternative that's better than migrating?
- Is this application needed at all?
- What cloud-native services could improve it?
- What's the total cost of ownership in cloud?
Migration Planning
Prioritisation
Migrate in waves, not all at once. Start with lower-risk, less-critical applications. Build experience and confidence before tackling core systems.
Dependencies
Map application dependencies. Applications that heavily integrate should migrate together. Plan for hybrid connectivity during transition.
Landing Zone
Before migrating applications, establish cloud foundation: network architecture, identity, security controls, governance. A well-designed landing zone enables consistent, secure migrations.
Testing Strategy
Plan thorough testing: functional, performance, security. Establish acceptance criteria before migration. Define rollback procedures.
Execution Considerations
Data Migration
Data is often the hardest part. Large datasets take time to transfer. Plan for delta sync during cutover. Validate data integrity thoroughly.
Cutover Planning
Define the cutover approach for each application:
- Big bang: Switch everything at once. Higher risk, shorter transition.
- Phased: Migrate components gradually. Lower risk, longer hybrid period.
- Parallel run: Run both environments, switch traffic. Highest cost, lowest risk.
Communication
Keep stakeholders informed. Set expectations about outages, changes, and timelines. Migration affects users - manage the change.
Common mistakes: Underestimating data transfer time. Ignoring licensing changes. Assuming cloud will be cheaper without architecture changes. Skipping proper testing.
Post-Migration
Optimisation
Initial sizing is often wrong. Monitor actual usage and right-size resources. Implement auto-scaling. Consider reserved instances for predictable workloads.
Decommission
Once migration is validated, decommission on-premise infrastructure. Don't pay for both environments longer than necessary.
Continuous Improvement
Rehosted applications can be modernised over time. Cloud migration isn't the end - it's the beginning of cloud-native transformation.
Summary
Cloud migration requires strategy, not just technical execution. Use the 7 Rs to categorise workloads and choose appropriate approaches. Start with thorough assessment. Plan migration waves from low to high risk.
Invest in landing zone design upfront. Test thoroughly before cutover. Optimise after migration. Remember: the goal isn't just running in cloud - it's capturing cloud benefits.