Moving to cloud datacenters means replacing your on-premises servers with rented computing power, storage, and networking from a provider like AWS, Microsoft Azure, or Google Cloud

The shift is not a single event but a sequence of decisions about which workloads move first, how to handle data that cannot move, and what happens to staff who managed physical hardware. Most organizations take six months to three years depending on their size and complexity. The actual technical work — migrating databases, rewriting applications, testing — is often the easier part. The harder part is planning what stays behind, training people to work differently, and managing the cost surprises that come when you first see your cloud bill.

This guide walks through what actually needs to happen, in the order it usually happens, so you can understand what your organization is signing up for.

Key Takeaways

  • You need an inventory of every application, database, and server you currently run, plus documentation of how they talk to each other and what they do.
  • Some workloads move easily to the cloud; others require rewriting code or redesigning how data flows, which takes months and costs money upfront.
  • Your team needs training on cloud tools and practices before migration begins, not after, because cloud infrastructure works differently than on-premises servers.
  • You must plan for hybrid operation — some systems in the cloud, some on-premises — for months or years, which means managing two separate environments.
  • Cloud costs are unpredictable at first because you are paying for resources you use rather than hardware you bought, so budget for monitoring and optimization work.

Audit what you actually run and how it connects

Before you move anything, you need to know what you own. This sounds obvious but most organizations discover they have forgotten applications, undocumented databases, or systems that talk to each other in ways nobody wrote down. A cloud migration fails when you move 90 percent of your infrastructure and the 10 percent you forgot brings everything down.

The audit includes: every server and what runs on it, every database and who accesses it, every application and which other systems it depends on, every network connection between systems, and every external service you pay for or connect to. You also need to know the age of each system, when it was last updated, and whether the people who built it still work there. Old systems are often the hardest to move because the code is outdated, the original developers are gone, and nobody wants to touch them.

This work takes weeks or months depending on your size. Tools like CloudMapper, Cloudcraft, or your cloud provider's own assessment tools can help, but they find what is running — they do not tell you what it does or why. That part requires talking to the people who use and maintain each system.

Categorize workloads by how hard they are to move

Not everything moves the same way. Cloud providers use a framework called the "six Rs" to sort workloads: rehost (move as-is), replatform (move with minor changes), refactor (rewrite to use cloud features), repurchase (switch to a cloud-native alternative), retire (turn it off), or retain (keep it on-premises). Most organizations end up using all six.

Rehosting is fastest: you take a server running Windows or Linux and move it to a virtual machine in the cloud. This works well for applications that do not need to scale, do not process huge amounts of data, and do not need to talk to other cloud services. Replatform means you move the application but change how it runs — for example, moving a database from your own server to a managed database service like AWS RDS or Azure SQL Database. This takes longer but costs less to operate because the cloud provider handles backups, updates, and scaling.

Refactoring means rewriting the application to use cloud-native features like containers, serverless functions, or managed message queues. This takes the longest and costs the most upfront, but it usually costs the least to run and scales better. Repurchasing means abandoning your old system and buying a cloud-based alternative — for example, replacing your on-premises email server with Microsoft 365. Retiring means turning off systems nobody uses anymore. Retaining means accepting that some systems stay on-premises, either because they are too expensive to move or because they need to stay close to hardware or local networks.

Plan your network and security architecture in the cloud

Cloud infrastructure requires different security thinking than on-premises servers. In your datacenter, you probably have a perimeter — a firewall that controls what comes in and out, and everything inside is somewhat trusted. Cloud providers do not work that way. You build security at the application level, the data level, and the network level, and you assume nothing is trusted by default.

You need to decide how your cloud environment connects to your on-premises systems during the transition. Most organizations use a VPN (virtual private network) or a dedicated connection like AWS Direct Connect to create a secure tunnel between their datacenter and the cloud. This lets applications in the cloud talk to databases still on-premises, and it lets your employees access cloud resources as if they were local. This hybrid setup is not permanent — it is a bridge while you migrate — but it usually lasts longer than you expect.

You also need to decide on your cloud network architecture: how many separate environments you will have (development, testing, production), how traffic flows between them, and how you will handle disaster recovery if a cloud region goes down. These decisions affect cost, performance, and security, and they are hard to change later.

Train your team on cloud tools and practices before you start moving

Cloud infrastructure is managed differently than on-premises servers. Instead of logging into a server and running commands, you write code or use a web console to define what infrastructure you want, and the cloud provider builds it for you. This is called infrastructure-as-code, and it requires different skills and different thinking.

Your operations team needs training on the cloud provider's tools — AWS Console, Azure Portal, or Google Cloud Console — and on practices like containerization, serverless computing, and managed services. Your developers need to learn how to write applications that work in the cloud, which often means using APIs and services they have never used before. Your security team needs to understand cloud-specific threats and how to monitor and control access in a cloud environment.

This training should happen before migration begins, not after. If your team learns on the job, your first migrations will be slow and expensive, and you will make mistakes that cost money to fix. Most cloud providers offer free training and certifications. AWS, Microsoft, and Google all have learning paths for different roles.

Migrate workloads in waves, starting with the easiest

You do not move everything at once. You pick a workload that is easy to move, move it, make sure it works, and then move the next one. This approach — called a phased migration — lets you learn from each move and fix problems before they affect critical systems.

The first wave usually includes non-critical applications that are easy to rehost: development environments, test systems, or applications that do not talk to many other systems. These moves teach your team how to use the cloud provider's tools, how long migrations actually take, and what problems come up. The second wave includes more complex applications, and the third wave includes your most critical systems.

Each migration requires testing. You move the application, run it in the cloud, and verify that it works the same way it did on-premises. This testing usually takes weeks. You also need a rollback plan — a way to move back to on-premises if something goes wrong. Most organizations keep the old on-premises system running until they are confident the cloud version is stable.

Manage hybrid operations and unexpected costs

While you are migrating, you are running two separate environments: some systems on-premises, some in the cloud. This hybrid state is expensive and complicated. You are paying for on-premises hardware that is no longer fully used, and you are paying for cloud resources that are not yet optimized. Your team has to manage both environments, which means more work, not less.

Cloud costs are also unpredictable at first. You pay for what you use — compute time, storage, data transfer — and if you do not monitor closely, your bill can surprise you. A single misconfigured application that transfers large amounts of data between regions can cost thousands of dollars a month. A database that is not indexed properly can consume far more compute power than expected. Most organizations budget for a 20 to 40 percent cost overrun in the first year, and they hire someone to monitor and optimize cloud spending.

The hybrid phase usually lasts longer than planned. You finish migrating applications faster than you expected, but you keep the on-premises environment running as a safety net. Eventually you turn it off, but that decision is harder than it sounds because it means committing fully to the cloud and accepting that you cannot go back.

Plan for ongoing management and optimization

Moving to the cloud is not a project with an end date. Once you are fully in the cloud, you still need to manage infrastructure, apply security patches, monitor performance, and optimize costs. This work is different from managing on-premises servers, but it does not go away.

You need processes for deploying new applications, updating existing ones, backing up data, and recovering from failures. You need monitoring to know when something is wrong before your users do. You need security controls to prevent unauthorized access and to detect when something suspicious is happening. You need cost management to make sure you are not paying for resources you do not use.

Many organizations hire a cloud architect or a cloud operations team to handle this work. Some use managed services from their cloud provider or from third-party companies that specialize in cloud management. The cost of this ongoing work is often higher than people expect, so budget for it from the start.

Frequently Asked Questions

How long does a full migration to the cloud usually take?

Most organizations take one to three years depending on size and complexity. A small company with a few applications might finish in six months. A large enterprise with hundreds of applications, legacy systems, and complex integrations might take five years or more. The timeline depends on how many workloads you migrate in parallel, how much rewriting is required, and how much testing you do.

Do we have to move everything, or can we keep some systems on-premises?

You can keep systems on-premises permanently if they make sense to keep there. Some organizations run databases on-premises and applications in the cloud. Some keep legacy systems on-premises and move only new applications to the cloud. This is called a hybrid or multi-cloud strategy, and it is common. The trade-off is that you have to manage two environments instead of one.

What happens to our IT staff when we move to the cloud?

Your team's role changes but does not disappear. Instead of managing physical servers, they manage cloud infrastructure, monitor applications, handle security, and optimize costs. Some staff may need retraining or may choose to leave. Most organizations find they need the same number of people, just with different skills. Some roles like server maintenance disappear, but new roles like cloud architect and cloud security engineer appear.

Will moving to the cloud save us money?

It depends on what you are comparing. Cloud usually costs less than building and maintaining your own datacenter, especially for small and medium organizations. But it can cost more than running old on-premises hardware that you already paid for. The savings come from not having to buy new hardware, not having to pay for physical space and power, and not having to hire staff to manage infrastructure. The costs come from paying for cloud resources you use, from rewriting applications, and from the work of migrating.

What if we change our minds and want to move back to on-premises?

Moving back is possible but expensive and time-consuming. You would have to buy hardware, rebuild your on-premises infrastructure, and migrate applications again. Most organizations do not do this. Instead, they commit to the cloud and work through the problems that come up. If you are worried about being locked into a cloud provider, you can design your applications to be portable — using containers and avoiding provider-specific services — but this adds complexity and cost.