What Is Cloud Migration?

Breaking Down What Cloud Migration Means

Cloud migration is the process of moving a business’s data, applications and IT workloads from where they run today into a cloud environment. In most cases “where they run today” means servers in a comms cupboard or a small server room on site. It can also mean moving from one cloud provider to another, or bringing some systems back out of the cloud.

If you have ever asked what cloud migration actually means for a normal business, the simple answer is this: the systems your team uses every day stop depending on hardware you own and maintain, and run instead on infrastructure provided and managed by a cloud platform such as Microsoft Azure or Microsoft 365. Staff still open the same files, use the same line-of-business software and send email the same way. What changes is where all of that lives, who looks after the hardware underneath it, and how easily it can be reached from outside the office.

It helps to be clear about what cloud migration is not. It isn’t simply buying a subscription and hoping for the best, and it isn’t only copying files from a server to a shared drive online. A proper migration looks at what each system does, who depends on it, how it connects to everything else, and how it will be secured and supported once it has moved. That planning is what separates a migration that quietly improves the business from one that causes weeks of disruption.

For most small and medium-sized businesses, cloud migration is one of the most practical parts of a wider digital transformation. It is often the step that makes the other changes possible, from secure remote working to better use of data.

What Actually Moves to the Cloud?

A migration can cover a lot, or very little, depending on the business. It usually falls into two broad areas.

The first is data. When people ask what cloud data migration is, they mean moving stored information, such as shared files, email mailboxes, databases and archives, from local storage into cloud storage. This sounds simple, but the detail matters. File permissions need to carry across correctly, folder structures often need tidying before they move, and large volumes of data need to be transferred in a way that doesn’t choke the office internet connection or leave people working from two different copies of the same file.

The second is applications. Cloud application migration means moving the software itself, whether that is an accounts package, a practice management system, a CRM or a bespoke database. Some applications move across easily. Others were built years ago to run on a specific server and need changes, an upgrade, or replacing with a cloud-based alternative. Finding out which is which is a large part of the early planning work.

Alongside data and applications, businesses often move desktops and user environments too. Hosted virtual desktops let staff log into the same working setup from any device, which is useful for teams split between the office and home.

Types of Cloud Migration

There are a few different types of cloud migration, and most businesses will recognise themselves in at least one of them.

Why Cloud Migration Is Important

The main reason cloud migration matters is that on-premise infrastructure has a hidden cost that grows every year. Servers age, warranties expire, operating systems reach end of support, and the one person who knows how everything was set up eventually moves on. We have written before about the hidden cost of legacy systems, and much of that cost is exactly what a well-planned migration removes.

Flexibility is the next big factor. Cloud platforms let a business add storage, users or computing power when it needs them, and scale back when it doesn’t, without buying new hardware each time. For a growing business, or one with seasonal peaks, that changes how IT spending works: large, occasional capital costs become a predictable monthly cost that follows the size of the business.

Resilience is another reason that is easy to underrate until something goes wrong. A server failure, a flood, a break-in or a power cut at the office can stop a business that relies on one local machine. Cloud platforms are built with redundancy across multiple data centres, which makes it far easier to keep running through disruption. It is worth reading our piece on disaster recovery in the cloud era, because moving to the cloud doesn’t remove the need for proper backup, it just changes how it is done.

Security also improves when a migration is done properly. Major cloud platforms invest far more in physical and technical security than any SME could on its own. That said, the cloud provider secures the platform, while the business is still responsible for who can access its data and how. This is why identity and access controls, covered in our article on identity and access management, sit at the centre of every migration we plan.

Benefits of Cloud Migration

• Lower upfront hardware and replacement costs
• Predictable monthly IT spending
• Easy scaling as the business grows
• Secure access for staff from anywhere
• Better resilience and business continuity
• Stronger security baselines from leading platforms
• Less time spent maintaining ageing servers
• Faster access to new tools and features
• Simpler collaboration across teams and sites
• A solid foundation for wider digital transformation

Cloud Transformation vs Cloud Migration

The two terms are often used as if they mean the same thing, but there is a useful difference between them.

Cloud migration is the move itself: taking what you have today and getting it running reliably in the cloud. Cloud transformation is what a business does once it is there, changing processes, adopting new tools and rethinking how work gets done because the cloud now makes it possible.

A business can migrate without transforming. Plenty of organisations lift their servers into the cloud and carry on exactly as before, which is a perfectly sensible first step. Transformation tends to follow when the business starts asking better questions, such as whether a manual process could now be automated, or whether data from two systems could finally be joined up. In short, migration changes where your systems live, and transformation changes how your business uses them. Sentinel’s Digital Transformation Planning service picks up where migration leaves off.

What Is a Cloud Migration Strategy?

A cloud migration strategy is the plan that decides what moves, in what order, and how each system is treated along the way. Without one, migrations tend to drift, costs rise, and important dependencies get missed until something breaks.

A good strategy starts with the business, not the technology. What is the migration meant to achieve? Lower costs, better remote working, replacing an ageing server, meeting a compliance requirement? The answer shapes every decision after it. From there, each application and dataset is assessed and given its own approach. Our Technology Strategy & Development service is where this thinking usually begins.

What Are the 7 Rs in Cloud Migration Planning?

The 7 Rs are a widely used way of deciding what to do with each system during a migration. Rather than treating everything the same way, each workload is placed into one of seven categories.

Retire. The system is no longer needed and is switched off rather than moved. Most businesses find at least a few of these once they look closely.

Retain. The system stays where it is for now, usually because it isn’t ready to move or has a good reason to remain on site.

Rehost. Often called “lift and shift”, the system moves to the cloud largely unchanged. This is usually the fastest option.

Relocate. A variation of rehosting where whole virtual environments are moved to a cloud platform without changing the underlying setup.

Replatform. Small changes are made during the move to take advantage of the cloud, such as switching to a managed database service, without rewriting the application.

Repurchase. The existing software is replaced with a cloud-based (SaaS) alternative, for example moving from an on-site email server to Microsoft 365.

Refactor. The application is redesigned or rebuilt to work natively in the cloud. This takes the most effort but can deliver the most long-term benefit.

For most SMEs, the majority of systems fall into retire, rehost or repurchase. Refactoring is usually reserved for bespoke software that is central to how the business operates.

The Microsoft Cloud Migration Framework

Because so many UK businesses already rely on Microsoft 365, Microsoft’s own guidance is a useful reference point. The Microsoft Cloud Adoption Framework sets out a structured approach to moving into Azure and Microsoft’s wider cloud, covering the journey from defining the business reasons for moving, through planning and preparing the environment, to migrating, then governing, securing and managing what has moved.

The framework is detailed and written with larger organisations in mind, but its core message suits businesses of any size: agree why you are moving, get the foundations right before the first workload goes across, and treat security and governance as part of the project rather than something added afterwards. As a Microsoft partner, Sentinel uses the same principles, scaled to fit SME budgets and timescales. If Microsoft 365 is part of your move, our Microsoft 365 Support & Management service covers what happens after migration day.

How to Do Cloud Migration: The Process Step by Step

1. Assess what you have

Start by listing every server, application, dataset and user, and how they connect to each other. This is where hidden dependencies are found, such as an old reporting tool that quietly relies on a file share nobody thought about. It is also where software asset management pays for itself, because licensing often changes when software moves to the cloud.

2. Build the plan

Apply the 7 Rs to each system, decide the order of migration, and agree timings with the business. Low-risk systems usually go first, so any lessons are learned before business-critical ones move. A clear plan with owners and dates is what keeps a migration on track, which is why we treat it as a formal project through our Project Management & Implementation service.

3. Prepare the cloud environment

Before anything moves, the destination has to be ready. That means setting up accounts, networking, identity and access controls, security policies and backup. Your internet connection matters here too, since everything will now travel over it. Our connectivity solutions make sure the office link is up to the job.

4. Migrate in stages

Data and applications are moved in planned waves, often outside working hours, so staff are not disrupted. Where possible, old and new systems run side by side for a short period, giving a safe fallback if anything needs adjusting.

5. Test and validate

Every migrated system is checked before users rely on it. We cover this in more detail in the next section, because it is the step most often rushed.

6. Train, optimise and manage

Once live, staff need to know what has changed and how to get the best from it, which is where training and knowledge transfer comes in. Costs and performance should also be reviewed regularly, since cloud spending can creep up without anyone noticing. Our guide to cloud cost optimisation explains how to keep it under control.

What Is Cloud Migration Testing?

Cloud migration testing is the process of checking that systems work correctly after they move, before the business depends on them. It sounds obvious, but it is where many migrations cut corners, usually because the team is under time pressure and the system “looks fine”.

Good testing covers several things. Data is checked to make sure it arrived complete and unchanged, with the right permissions. Applications are tested to confirm they behave as they did before, including the less common tasks that only happen at month end or year end. Performance is measured to make sure the system is at least as fast as it was on site. Security is tested to confirm that only the right people can reach the right data. Finally, a small group of real users should try the system as they would on a normal working day, because they will spot problems that technical tests miss.

Testing also includes checking the way back. If something serious goes wrong on migration day, there should be a clear, tested plan to return to the old system while the issue is fixed.

How Long Does Cloud Migration Take?

There is no single answer, because it depends on how many systems are moving, how complex they are, and how much data is involved. As a rough guide:

A small business moving email and shared files into Microsoft 365 can often be migrated within a few weeks, including planning and testing. A business with several servers and one or two line-of-business applications will more typically take two to six months, as each application needs its own assessment and testing. Larger or more complex environments, especially those involving bespoke software or strict compliance requirements, can run for six months to a year or more, usually in phases.

The actual moving of data is rarely what takes the time. Planning, preparing, testing and bringing staff along with the change are what decide the timeline, and they are also what decide whether the migration succeeds.

Moving From Cloud Back to On-Premise

Migration from cloud to on-premise, sometimes called cloud repatriation, is less common but worth understanding. Some businesses bring certain workloads back on site because cloud costs grew higher than expected, because an application needs very low latency, or because of data residency rules in their sector.

In most cases, the root cause is not the cloud itself but how it was set up. Workloads that were lifted and shifted without any changes can cost more in the cloud than they did on site, and a cost review often fixes the problem without moving anything back. Where repatriation does make sense, it follows the same careful process as any other migration: assess, plan, prepare, move in stages, and test. For many businesses, the result ends up being a hybrid setup, keeping each workload where it works best.

What Are Cloud Migration Services?

Cloud migration services are the professional support a business brings in to plan, carry out and manage a move to the cloud. For an SME without a large in-house IT team, this is usually the difference between a smooth migration and a painful one.

A cloud migration project delivered by a partner typically includes an assessment of your current environment, a migration strategy and plan, preparation of the cloud environment, secure transfer of data and applications, testing, user support on go-live, and ongoing management afterwards. The last part matters more than it seems. Moving to the cloud is not a finish line, and systems still need monitoring, patching, securing and reviewing once they are there.

Sentinel’s Cloud Migration & Management service covers the full journey, from the first assessment through to looking after your environment once it is live, as part of our wider cloud services. Every migration is planned with security built in, in line with our Cyber Essentials Plus certification. You can see how we have helped other businesses in our case studies.

Getting Started With Cloud Migration

You don’t need a detailed technical plan before starting the conversation. The most useful first step is usually a simple question: what is your current setup costing you, in money, time or risk, and what would you like it to do better?

The answer often points to an obvious starting place. That might be an ageing server that is due for replacement, email that still runs on an old system, or staff who struggle to work properly away from the office. Solving that one problem well, with a clear plan behind it, tends to build confidence for the next step.

Sentinel works with businesses across Hampshire, Dorset, Wiltshire, Surrey and Berkshire, with local cloud support in areas including Bournemouth, Southampton and Surrey. As a Cyber Essentials Plus-certified provider, we plan every migration with security in mind from day one, not added once the move is done.

If you are thinking about moving to the cloud and aren’t sure where to begin, get in touch with Sentinel to talk through your current setup and what could sensibly move first.