Migration Planning Guide

A successful cloud migration follows a structured process. Skipping phases or rushing through planning is the most common reason migrations go over budget, miss deadlines, or cause extended downtime. This guide walks through the four phases of a well-executed migration, along with pitfalls to avoid at each stage.

Phase 1: Assess

The assessment phase is about understanding what you have and what needs to move. Expect this phase to take two to four weeks for a small business with 20 to 100 users.

1. Inventory everything. Document all servers, applications, databases, file shares, printers, and network devices. Include shadow IT: cloud services that departments adopted without IT involvement.
2. Measure performance baselines. Record CPU, memory, disk, and network utilization for at least two weeks. These baselines will help you right-size cloud resources instead of guessing.
3. Identify dependencies. Map which applications connect to which databases, which services depend on which servers, and which systems communicate with external partners.
4. Classify workloads. For each system, determine the migration strategy:
   • Rehost (lift-and-shift): Move the server as-is to a cloud VM. Fastest, but you inherit all the existing technical debt.
   • Replatform: Make minor adjustments during migration (upgrade OS, switch to managed database). Moderate effort for meaningful improvements.
   • Replace: Swap the application for a SaaS equivalent. Often the best long-term choice, but requires change management.
   • Retain: Keep on-premises. Some systems are not worth migrating due to cost, complexity, or vendor limitations.
   • Retire: Decommission. You will almost always find systems that nobody uses anymore.
5. Estimate costs. Use the AWS Pricing Calculator or Azure Pricing Calculator to model your monthly cloud spend. Add 20% buffer for the first year while you optimize.

Phase 2: Plan

Planning translates your assessment into a concrete project. This phase typically takes two to three weeks.

1. Define the migration order. Start with lower-risk, less-critical systems. Migrate email or file storage before moving your primary line-of-business application. Each successful migration builds team confidence and reveals issues while stakes are lower.
2. Set a timeline. Be realistic. A small business migration (five to ten workloads) typically takes six to twelve weeks from start to finish. Trying to compress that into two weeks leads to mistakes.
3. Plan for downtime. Zero-downtime migration is possible but expensive. For most small businesses, scheduling migrations during evenings or weekends with clear communication is more practical. Define your maintenance windows in advance.
4. Build your rollback plan. For every system you migrate, document exactly how to revert to the previous state. Keep on-premises systems running in parallel for at least one to two weeks after migration. Never delete the original until you are confident the cloud version is stable.
5. Assign responsibilities. Identify who is managing each workload migration, who is testing, and who approves the cutover. Small teams may have one person wearing multiple hats, but the roles still need to be defined.
6. Communicate with stakeholders. Create a communication plan that tells users what is changing, when, and what they need to do. Send reminders before each migration window.

Phase 3: Migrate

Execution follows the plan. The key to this phase is discipline: stick to the process, test rigorously, and do not skip validation.

1. Set up the cloud environment first. Configure networking (VPC/VNet), security groups, identity management, and monitoring before migrating any workloads. Rushing this step creates security gaps that are hard to fix later.
2. Migrate in waves. Group related systems together and migrate them as a unit. Test each wave thoroughly before starting the next one.
3. Test after every migration. Verify that applications work correctly, data is intact, users can authenticate, and performance meets baseline expectations. Have end users test real workflows, not just log in.
4. Monitor closely for the first 48 hours. Watch for performance issues, authentication failures, application errors, and user complaints. Many problems surface only under real production load.
5. Document changes. Update network diagrams, runbooks, and support documentation as you go. Waiting until the end means you will forget critical details.

Phase 4: Optimize

Migration is not finished when the last server is in the cloud. The optimization phase is where you realize the full value of cloud computing.

1. Right-size resources. After 30 days of production data, review your cloud resource utilization. Most organizations over-provision during migration and can reduce costs by 20 to 40% by resizing instances.
2. Implement cost controls. Set up billing alerts, tag resources by department or project, and review spending weekly for the first three months. Cloud costs can escalate quickly without visibility.
3. Enable auto-scaling where appropriate. For workloads with variable demand, auto-scaling reduces costs during quiet periods and handles spikes without manual intervention.
4. Review security posture. Run a cloud security assessment 30 days after migration. Check for overly permissive access, unencrypted storage, public-facing resources that should be private, and missing logging.
5. Decommission old infrastructure. Once you have confirmed everything is stable, power down and eventually decommission on-premises systems. This is where you realize the cost savings from reduced hardware, power, and cooling.

Common Pitfalls

• Underestimating bandwidth needs. What felt fast on a local network will feel slow over the internet if you have not planned for adequate bandwidth.
• Ignoring licensing. Some software licenses do not transfer to the cloud. Verify before you migrate, not after you get an audit notice.
• No rollback plan. If something goes wrong and you have already decommissioned the original, you have no safety net.
• Migrating everything at once. Big-bang migrations have a much higher failure rate than phased approaches.
• Forgetting about DNS and email. DNS propagation and mail flow changes need careful planning and testing. A misconfigured MX record can stop all incoming email.
• Skipping user training. The technology may change, but the people using it need to know what is different and how to get help.