Cloud Migration Types: Advantages and Disadvantages

Businesses are increasingly adopting digital transformation initiatives related to infrastructure, data, and applications. Cloud migration plays a critical role in these processes. 

Put simply, cloud migration means moving all or part of your company’s business data, processes, operations, and applications into the cloud. This usually means transferring data, workloads and services to the cloud by recreating vital infrastructure elements utilizing cloud platform capabilities. The benefits are clear:

  • Decreased hosting, compute, database, networking, and administration costs: In the cloud, you no longer have to keep your own physical servers running. On top of that, you no longer need to have a huge team of professionals supporting your on-premise infrastructure. 
  • Agility and scalability: Cloud-based services can scale to cope with fluctuations in user demand, while your teams can collaborate on projects and maintenance from anywhere.
  • Disaster recovery: Cloud-based backup and recovery are more efficient, better maintained, and updated more regularly, making your operations more robust.
  • Improved security: The cloud provider of your choice will take on a huge part of the security responsibility that was previously on your side, like the security of your infrastructure. It’s called the ‘shared responsibility model’.
  • Reduced carbon footprint: Using aggregated cloud computing resources helps to reduce carbon dioxide usage, eliminating 1 billion tons of carbon emissions by 2024, as reported by the IDC

But, the concept of cloud migration hides a significant amount of granularity. Not only can you carry out your migration in stages and at different levels, but you also need to optimize your cloud use. Get your strategy right and you’re winning, but get it wrong and you have a budget problem. It’s no wonder that Flexera’s 2021 State of the Cloud report revealed that while cloud migration is increasing, cloud spending and efficiency are a major concern for most decision-makers.

That efficiency begins at the start, with your migration plan. This article will explore the different cloud migration types and their pros and cons in order to give you a running start when considering your options. 

A Quick Overview of Application Migration Approaches

The choice of the approach to cloud migration can vary quite substantially in different organizations and businesses. The decision on how to handle the migration in your organization, first of all, will depend on your business’ motivations and objectives. Knowing precisely what you want to achieve with cloud migration is the first step towards building a specific and detailed path to fulfill it.

Above that, the approach to cloud migration depends on what your current on-premise infrastructure looks like. After a thorough audit of the current applications’ architecture issues, gaps and risks, it becomes quite clear which of your applications need to be retired/retained and which need to go through a migration phase. Both components, cloud migration goals and infrastructure state, will shape the cloud migration strategy for your business. 

After you’ve clearly outlined your cloud migration goals and assessed your current as-is architecture, you can define your cloud strategy on your own or get expert help from cloud partners, like Avenga. 

The most common cloud migration approaches are described here, ordered by the complexity and corresponding level of investment and expertise required. Each of the approaches has its advantages and disadvantages, and understanding what to expect from each approach can help you adjust your migration strategy more specifically to your needs.

Rehost:  Rehosting is often called “lift and shift” because you move an entire application from your internal servers and place it in the cloud without any changes.

Replatform: Your applications and data are migrated to a cloud platform, utilizing some of the PaaS services of the cloud platform (e.g., managed data stores or messaging middleware). The overall system architecture will remain the same.

Repurchase: In this type of migration, a new SaaS solution replaces the existing one. 

Refactor: Using this approach, you partially or fully redesign and optimize an existing application to improve performance and reduce costs. 

Re-architect: This type of migration takes refactoring to the next level. It includes an architectural redesign that takes advantage of both multi-cloud and native cloud environments. 

Rebuild: This involves redeveloping an app or solution from scratch, entirely in the cloud, while taking advantage of the latest tools and frameworks.

Retire: Sometimes, a cloud migration plan will reveal which applications can be discontinued. Retiring an application requires data to be archived and cleaned up. An application can also be withdrawn when part of its functionality gets refactored, re-architected, rebuilt, or repurchased.

The pros and cons of different cloud migration approaches

Different cloud migration approaches have advantages and disadvantages, and understanding what to expect from each type can help you adjust your migration strategy to your unique needs.

The rehost (lift and shift) approach

At this level of migration, your applications, data, and servers are moved to the IaaS tier of the cloud platform without major alterations. As a result, you continue to deal with servers, networking and per-server maintenance, only utilizing virtual machines and networking services of the cloud provider. Except, you don’t take full advantage of the capabilities of the cloud. If you have an application located on a traditional server, you lift it along with all the necessary runtimes and software. You can either virtualize the bare-metal environment or migrate the existing virtual environment and then install the app within a virtual server, like Amazon EC2 or Azure Virtual Machine, and deploy the application within that.  

Advantages: Rehosting is the cheapest and easiest way to migrate to the cloud. It requires minimum time and expertise, and mitigates the risk of breaking anything by messing with your application’s code.

Disadvantages: Although rehosting is a comparatively simple approach, failures due to complex application dependencies or long outage periods might occur. If a virtual server goes down, your application goes down, similar to traditional server behavior. Additionally, even if a rehost cloud migration succeeds, you won’t be taking advantage of all the powerful cloud-native capabilities.

→ Read more about lift and shift

The replatform approach

With replatforming, you migrate the application from a traditional server, make configuration and environment-specific changes, such as containerization of the service, state offload and distribution, session-management layer re-engineering, etc., and then migrate it to the cloud without modifying the application itself.

For example, say you have a legacy application running on a traditional server. You can replatform and utilize the advantages of the new cloud PaaS infrastructure. And, cloud architects can modify the way an application interacts with a database so it can take advantage of automation opportunities and a more varied database infrastructure. 

In case you are moving an on-premises SQL database to a cloud-managed database, like AWS RDS (Relational Database Service), it may require a small number of changes that are usually limited to the application’s configuration. However, the wins are significant: the reduction of the operational burden, out-of-the-box mirroring and fault-tolerance, as well as other benefits.

Advantages: Replatforming doesn’t require a massive investment in time or money and several SaaS options provide replatforming solutions. The replatform approach allows you to improve a part of an application while the rest of the application remains operational in the cloud.

Disadvantages: Replatforming applications can sometimes get out of hand. It can vary from deploying just a few small changes to the application or service, up to a complete re-architecture of some components. Hence, replatforming might involve risks, such as errors in the code or configuration. You need to establish a thorough plan of which features you want to change beforehand and those changes should be very carefully implemented.

The repurchase approach

Repurchase means moving from purchased on-premise software to a cloud-based SaaS equivalent. For instance, transferring from CRM to Salesforce, or transfering the backend code that was hosted on premises to the private cloud data server. 

Repurchasing software is a good option if you want to harness the scalability, flexibility and agility capabilities offered by cloud solutions.

→ Find out more about ready-made solutions from Avenga

Advantages: Since the product you use is already configured for the cloud, you don’t need to spend time and effort configuring it yourself. More importantly, repurchasing can be cheaper than refactoring, as we’ll see next.

Disadvantages: Sometimes the repurchase approach can be more expensive than hosting the app or service on your own premises. It also requires a high-speed bandwidth connection and a poor connection can be the cause of potential downtimes. What’s more, if your application is highly specialized and has unique features, repurchasing won’t be a viable option.

The refactor approach

Refactoring means re-engineering your application to become a cloud-native. For instance, you could migrate existing applications to virtual services or refactor relational and nonrelational databases into Amazon Aurora and Azure Cosmos DB.

The need to refactor is often induced by a business’ necessity that requires the need to add new functionalities and/or to easily scale up and down, which would be hardly achievable with the current service’s architecture.

Advantages: Refactored applications take advantage of cloud-native capabilities. From the long-term perspective, refactored software is much more cost-effective than a non-refactored app. They are quick, reusable, and allow on-demand provisioning.

Disadvantages: Refactoring has high initial costs and is time-consuming compared to other approaches.

The re-architect approach

Re-architecting optimizes an application and makes it more scalable, secure, accessible, fast and agile by modifying and extending its functionality. Such as, you could separate a monolithic application into many independent microservices that can be read, written, and executed independently. 

Advantages: While the refactoring approach involves restructuring the code, the re-architect approach is about changing the way the code is functioning, thus capturing the value of the business advantages that are independent of the legacy codebase. Basically, re-architecting is refactoring at a higher level. Re-architecting means moving the service into a fresh paradigm, in the meantime reducing the specific parts of code.

Disadvantages: Re-architecting is even more time-consuming than refactoring and requires a higher amount of initial effort. The code re-architecting may be complicated to carry out, which can potentially lead to bugs or security issues as the changes will be deployed to production. 

The rebuild approach

With rebuilding, you create your application directly in the cloud, taking advantage of all the tools available. The rebuild approach is often used when the new changes in the app require the code to be rewritten. In some cases it may be more challenging to read the old code than to build it from zero.  

Advantages: Building an application from the ground up will enable you to fully utilize everything the cloud has to offer. It is much easier to support and widen the app or service, when it is built in the cloud from scratch.

Disadvantages: It takes time and effort to get a new application off the ground. Rebuilding the app or service in the cloud may potentially introduce new bugs that developers haven’t encountered in the legacy app. 

The retire or retain approach

When you plan to migrate to the cloud, you may find that some applications are no longer necessary for your business and don’t need to be included in your migration plan. Alternatively, there may be applications that you use but don’t want to include in your migration for various reasons. The retire approach is used when the application or service is used infrequently or sporadically, and it’s not worth being rehosted, replatformed, or re-architected to the cloud. In this case, the app can be retained on the local servers.

Advantages: The retiring approach helps you free up space on your on-premises servers, clear out your infrastructure, and eventually reduce costs. Additionally, retiring obsolete business applications can deliver significant cost savings, as substantial amounts of software budgets are spent on app maintenance.

Disadvantages: If an application’s maintenance and support costs are much higher than the usefulness it brings and you’ve decided to retire it, then it might require energy and effort to build a useful app from scratch. 

After checking out the advantages and disadvantages of each approach, it is time you have a look at the collection of products and services that the top cloud providers recommend for the migration, in terms of the specific approaches your company would like to pursue. 

Here you can find a comparison of the top cloud data migration service providers, including AWS, Azure, and Google Cloud.

What to choose: Rehost, refactor, replatform, re-architect, rebuild, or retain/retire?

Your ideal cloud migration strategy will be a balance between cost, time, and performance. Some approaches result in excellent performance but might be time-consuming, while others will compromise on performance but allow quick migration when time is of the essence.

Your cloud migration strategy will guide your entire migration process, which can last for months or even years. A typical way to choose the right strategy is to conduct an Assessment and Discovery process. In this process, specialized staff make an inventory of your current systems and applications to determine how much time and effort is required, while keeping in mind your objectives and goals.

Cloud migration benefits with Avenga

A meticulous and well-thought-out cloud migration strategy can be the difference between getting the true benefits of the cloud and struggling with soaring cloud expenditures and inefficiency. A cloud migration services provider can play a crucial role in your success or your failure.

Avenga’s end-to-end cloud migration services can help you map out your existing instances and plan your move, whether you’re shifting to the cloud for the first time or expanding your present cloud deployment. We have a proven track record in cloud and other software solutions, meaning that we have a complete range of cross-technology expertise to offer. Not to mention, our vendor-agnostic approach means we’ll advise on the solution that’s right for you, independent of vendor or developer bias.

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