Dependency Mapping and Migration Sequencing
Dependency mapping is the process of discovering how applications, services, and hardware rely on each other. This is done during the assessment phase by building a complete inventory. Understanding these connections is essential because it prevents you from breaking services that are still on-premises when you move other parts to the cloud.
Once dependencies are clear, you organize workloads into migration waves. These are groups of applications moved in specific stages, often broken into smaller move groups for easier management. Grouping by dependencies minimizes service disruptions and ensures complex systems move only when the environment is ready. Choosing the right first-movers is a key strategy. These are low-risk applications with few dependencies, like stateless microservices, non-critical internal tools, or loosely coupled systems. Moving these first lets teams build Google Cloud knowledge safely.
Network and data consistency are major factors in deciding the migration order. You must account for network latency and ensure data stays synchronized between on-premises and the cloud. Establishing strong connectivity using Cloud Interconnect or Cloud VPN is crucial so migrated workloads can still talk to resources left behind. Before the final move, a Proof of Concept (POC) validates the plan. This small-scale test identifies edge cases and confirms data completeness and performance, lowering the risk for the final cutover.
Evaluation of Migration Methodologies and Validation Testing
The first step is the assessment phase, where teams build a comprehensive inventory and perform dependency mapping. This deep knowledge of how services connect helps avoid unexpected failures during the migration.
Migration Methodologies
You must choose the right migration strategy for each workload based on business goals. The main options are:
- Rehosting ("lift and shift"): moving the application exactly as it is.
- Replatforming: making small optimizations for the cloud.
- Refactoring: changing the code to use cloud-native features.
Selecting the correct method balances the need for speed with long-term efficiency.
Network and Dependency Planning
Network planning is vital for secure connectivity. This involves setting up Virtual Private Clouds (VPCs) and planning IP address management to prevent overlaps between on-premises and cloud networks. Dependency planning ensures connected services are moved in the correct order. A solid network foundation enables reliable communication between all resources.
Workload Testing and Validation
A Proof of Concept (POC) is used for validation of migration feasibility. It allows for workload testing protocols in a low-risk environment to check performance, scalability, and functional integrity. These tests help identify risks and estimate potential downtime. Rigorous validation ensures the application will work correctly after the final move.
Execution and Rollback Planning
The final plan organizes the move into batches or waves. Each wave contains a move group of related applications that must transition together to maintain service. Every step needs a rollback strategy in case of issues. Post-migration validation is the final check to confirm all data is complete and the new system is healthy.
Network Infrastructure Planning and Hybrid Connectivity
The Assess Phase involves building a full inventory and performing dependency mapping. This identifies which applications are "loosely coupled" and easier to migrate without breaking other systems, helping decide the migration order.
To link your data center to Google Cloud, you must choose a Hybrid Connectivity method.
- Cloud VPN provides a secure connection over the public internet, suitable for lower traffic volumes.
- Cloud Interconnect offers a direct physical connection for higher reliability and speed.
- Cross-Cloud Interconnect allows private links between different cloud providers like AWS or Azure.
Selecting the correct bandwidth ensures large-scale data transfers don't slow down operations.
Network Planning requires understanding that while Virtual Private Clouds (VPCs) are global, subnets are regional. You must plan new IP address ranges to avoid overlaps with your on-premises network. Using Cloud DNS with features like DNS peering or forwarding allows you to route traffic smoothly to new cloud locations, ensuring users can still find your services after the move.
A successful Migration Plan organizes workloads into migration waves based on business value and technical difficulty. Prioritizing non-critical workloads first lets your team build experience before moving mission-critical systems, reducing the risk of major outages. Each wave should include a clear rollback strategy.
Before the final move, create a Proof of Concept (POC) to validate the feasibility in a test environment. Workload testing includes functional testing to check if the application works and load testing to ensure it handles real-world traffic. These tests help estimate downtime and confirm the new network architecture meets performance and security goals.
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