Migration Strategies
6 Rs of Cloud Migration
Move applications to cloud without modifications. VM-to-VM migration or containerization without code changes. Fastest migration (weeks) with lowest risk. Limited cloud benefits - same operational overhead. Good for quick cloud presence or deprecated applications. Typical 10-30% cost savings. Optimize later after migration.
Minor cloud optimizations without changing core architecture. Examples: RDS instead of self-managed DB, ELB instead of HAProxy, managed services where possible. Faster than refactor with some cloud benefits. Typical 30-40% cost savings. Balance speed and optimization. Common for databases and middleware.
Move to different product, typically SaaS. Replace on-premises CRM with Salesforce, email server with Office 365, HR system with Workday. Reduces infrastructure management. License cost vs infrastructure savings. Data migration challenges. User retraining required. Common for commodity applications.
Redesign application for cloud-native architecture. Microservices, containers, serverless, managed services. Highest cloud benefit with 40-60% cost savings. Most expensive and risky. Required for scalability or modernization goals. Common for strategic applications. Enables DevOps and agility.
Decommission applications no longer needed. Review application portfolio and eliminate redundancy. Typical 10-15% of portfolio can be retired. Cost savings without migration effort. Reduces technical debt and security risk. Archive data for compliance. Identify replacement systems if needed. Low-hanging fruit for quick wins.
Keep on-premises for now. Not ready for migration (complexity, compliance, recent investment). Schedule for future migration wave. Maintain current environment. Typical 20-30% retained initially. Often mainframes, specialized systems, or recently upgraded. Hybrid architecture with retained systems.
Migration Patterns
Incrementally replace legacy system by routing functionality to new cloud system while keeping old system running. Named after strangler fig plant. Route new features to cloud, gradually migrate existing features. Reduces risk with parallel operation and easy rollback. Eventually decommission legacy when fully replaced. Ideal for large monoliths.
Build complete new environment (green) alongside existing (blue). Test thoroughly on green without production impact. Switch traffic from blue to green when ready. Keep blue for quick rollback. Fast cutover (minutes) with minimal downtime. Higher cost running two environments. Common for critical systems requiring high confidence.
Migrate in waves based on priority, risk, or business value. Start with non-critical applications to build experience. Progress to more critical systems. Spread risk and learning over time. Typical 6-24 months for complete portfolio. Quick wins for momentum. Can adjust strategy between waves based on lessons learned.
Migrate schema and data separately from application. Homogeneous (same DB engine) or heterogeneous (different engine). AWS DMS, Azure Database Migration Service for continuous replication. Minimize downtime with replication and cutover. Test data integrity and performance. Consider managed database services. Critical for stateful applications.
One-time bulk transfer vs continuous replication. Online (minimal downtime) vs offline (longer outage). Direct transfer, snowball devices for large datasets, or AWS DataSync/Azure Data Box. Validate data integrity post-migration. Consider data gravity and network costs. Keep source until validation complete.
Start with low-risk pilot application to validate approach, tools, and team skills. Prove cost model and performance. Build confidence and references. Typical small web app or internal tool. Document lessons learned. Adjust strategy for production migrations. Create playbooks and automation. Demonstrate success to stakeholders.
Migration Phases
Inventory applications, dependencies, and infrastructure. Understand current architecture and costs. Application discovery tools (CloudScape, Cloudamize) for automated assessment. Interview application owners. Document requirements and constraints. Calculate TCO comparison. Prioritize applications for migration. Identify quick wins and risks.
Choose migration strategy for each application (6 Rs). Design target cloud architecture with security, networking, compliance. Estimate costs and build business case. Create migration runbooks and playbooks. Plan wave groups and dependencies. Resource planning and skill assessment. Risk analysis and mitigation plans. Establish success criteria.
Execute migration per runbooks with pre-migration checklist, migration, and post-migration validation. Application migration with data synchronization. Infrastructure provisioning via IaC. Testing in cloud environment. Performance validation and tuning. Address issues with rollback procedures. Parallel run period for critical systems. Cutover planning.
Comprehensive testing post-migration including functional, performance, security, disaster recovery. User acceptance testing. Data integrity verification. Monitoring and alerting setup. Cutover communication and scheduling. DNS/routing changes. Decommission source environment after stabilization period. Document as-built architecture.
Post-migration optimization leveraging cloud capabilities. Right-size resources based on actual usage. Implement auto-scaling and cost optimization. Enhance security and compliance. Modernize applications incrementally. Monitor cloud spend and performance. Continuous improvement. Often 20-40% additional savings after optimization phase.
Migration Tools & Considerations
Centralized service to track application migrations across AWS and partner tools. Discover on-premises resources, group into applications, track migration status. Integration with AWS Application Discovery Service, Database Migration Service, Server Migration Service. Unified dashboard for portfolio migration. Free service tracking progress and providing visibility.
Hub for assessment, migration, and modernization to Azure. Discover and assess servers, databases, web apps, VDI. Server assessment tool, Database Migration Assistant, App Service migration assistant. Cost estimates and right-sizing recommendations. Track dependencies and group servers. Integrated migration execution tools.
Automated VM migration to Google Cloud from on-premises, AWS, or Azure. Streaming replication with minimal downtime. Test clones without impacting production. Automated validation and rollback. Supports Windows and Linux. Part of broader GCP migration tools including Database Migration Service and Transfer Service.
Understand application dependencies for grouped migration. Discover server-to-server communication, database connections, shared storage. Tools: AWS Application Discovery Service, Azure Migrate dependencies, ServiceNow. Avoid breaking applications by migrating dependent components together. Critical for microservice identification.
Understand license implications for cloud. Bring Your Own License (BYOL) vs new cloud licenses. Microsoft License Mobility, Oracle license audits, SQL Server licensing. Dedicated hosts for license requirements. License optimization opportunities (RDS reducing Oracle licenses). Calculate total cost including licensing.
Detailed plan for switching from source to target. Freeze periods, data synchronization, DNS changes, validation checkpoints, rollback triggers. Communication plan for stakeholders and users. Change windows and maintenance notifications. Dress rehearsals for critical migrations. Rollback procedures and criteria. Success criteria and go/no-go decisions.