Meet the challenge of migrating to the cloud

More than 70% of companies have now migrated at least some workloads into the public cloud, and momentum is increasing: more than two-thirds of companies surveyed in 2020 plan to increase their cloud adoption. Cost control, however, ranks as the most frustrating challenge. Without realistic project estimates and cost forecasts, I&O leaders will struggle to assess the progress and performance of cloud migration initiatives. Here’s what they should do.


This is a contributed article by David Wright, Senior Research Director at Gartner

 As organisations migrate applications to the public cloud, they continue to find challenges. Meeting these challenges effectively is the key to having a successful public cloud experience.  One of the negative outcomes that can occur is when costs get out of control.  There are six main ways that this can happen.

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The key to avoiding cost overruns starts with building a view of how different migration approaches compare, identifying the hidden costs of any migration, and facilitating cost revisions mid-migration. 

Select the right migration approach and align costs to project phases

The most critical early phase in a cloud migration project is application assessment. This phase will determine which cloud migration approach should be used for each application.

Under pressure to move quickly, many I&O leaders prioritise the “lift and shift” approach of moving workloads into the cloud without modifying them. But moving too quickly through application assessment often means failing to consider that, for many on-premises applications, the best “move” for the business may not be a move at all. Rather, it may be to rewrite and rerelease an application in a cloud-native way, or even to replace it entirely with a SaaS-based cloud alternative.

Broadly, Gartner defines five ways to migrate a workload to the public cloud:

  1. Rehost: “Lift and shift” your application from its current physical or virtual environment onto a cloud platform, making as few changes to the application and its runtime environment as possible.
  2. Revise: “Lift, shift and adjust” your application just enough to make it safer, easier and less costly to manage in the public cloud.
  3. Rearchitect: Materially alter or refactor the application toward a cloud-optimised architecture, making some use of cloud-native capabilities.
  4. Rebuild: Optimise for the cloud by rewriting the app from scratch, preserving core business logic and algorithms, but letting go of legacy code and rebuilding on cloud platforms and services.
  5. Replace: Replace an application with a third-party SaaS alternative, configuring or extending the SaaS environment to meet requirements, and (if necessary) migrating legacy data into the new environment.

The rehost and revise approaches often have the lowest migration and organisational transformation costs because they require the fewest changes to how applications are already deployed and managed on-premises. However, because these workloads are not adapted to the cloud, they tend to run less efficiently and require more manual support. This can often result in higher long-term total cost of ownership (TCO) than other cloud migration options.

In contrast, the rearchitect and rebuild approaches require more upfront investment. They usually take place in activities such as database replacement, refactoring code into container-based microservices, and the adoption of agile DevOps methodologies and twelve-factor app design. Organisations willing to make this investment typically are rewarded with lower operating costs, greater resilience and better long-term ROI.

Many organisations choose to replace some legacy applications with SaaS alternatives. Because moving to a SaaS application does not require the physical migration of workloads, the immediate migration costs for SaaS can be lower than other alternatives. I&O leaders should keep in mind, however, that the cost to migrate user accounts and data from previous systems, along with the cost to integrate the SaaS application with other enterprise systems, can be significant and must be properly accounted for. Moreover, moving to SaaS does not eliminate ongoing operational costs; these costs are simply transferred into the vendor’s software licensing price. Gartner is planning to look at these five strategies closely at the upcoming Infrastructure, Operations & Cloud Strategies Conference and focus on the balance of initial deployment speed and TCO.

Indirect cloud migration costs

I&O leaders should also call out in their estimate any key “indirect” costs tied to cloud migration that are not otherwise accounted for in other budgets or plans. The most important of these are the costs associated with transforming their organisation to operate effectively in the public cloud, and the residual (sunk) costs of existing data center resources that become less valuable as workloads transition into the cloud. These costs are frequently unavoidable but are just as frequently overlooked or underestimated.

Migrate in phases and revise your cost estimates as you go

While cost planning has its benefits, assumptions and industry averages must be replaced as soon as possible with accurate data based on the migration effort itself. I&O leaders will be more able to hone and improve their migration cost estimates over time if they structure their cloud migration initiative in iterative phases.

Work with the migration vendor to group applications into different clusters of workloads that will be migrated or modernised together. The first clusters to be migrated should be treated as “learning migrations.” They should include a selection of workloads diverse enough to determine the actual cost of different migration approaches but limited enough that mistakes and rework will not derail the full project schedule or costs.

Taking a methodical and comprehensive approach to cloud migration cost estimation and revision is a vital starting point. It will help I&O leaders set the right expectations within the organisation and facilitate what everyone seeking to migrate to the public cloud wants – a positive result.

David Wright is a Research Director at Gartner where he focuses on public, private and hybrid cloud infrastructure. His coverage includes infrastructure as a service (IaaS), platform as a service (PaaS), on-premises software-defined data centers and edge computing. Mr. Wright delivers advice to IT buyers on topics such as public cloud, hybrid, multicloud and cloud edge strategy, cloud sourcing and cost governance and has 30 years’ experience in the industry.