Navigating Cloud Migration: Choosing the Right Strategy

​Organizations are increasingly moving to the cloud due to a variety of factors, including the need for greater agility, scalability, cost-efficiency, and improved security. Cloud providers offer businesses access to a wide range of services and resources that can be quickly provisioned and scaled to meet changing business needs. 

Cloud migration is the process of moving an organization's data, applications, and other digital assets from on-premises infrastructure to a cloud computing environment. Migrating to the cloud offers many benefits, including greater flexibility, scalability, security, and cost savings. However, there are many different cloud migration strategies to choose from, each with its own unique set of benefits and challenges. 

When we talk about migrating a workload to the  Cloud, we're referring to the process of moving an application or workload to the cloud. In this article, we'll focus on the migration strategies for the AWS Cloud.

There are seven migration strategies that we call the 7 Rs, which are:

• Retire
• Retain
• Rehost
• Relocate
• Repurchase
• Replatform
• Refactor or re-architect

 
It's really important to select the right migration strategies for a large migration. You might have already selected the strategies during the mobilize phase or during the initial portfolio assessment. In this section, we'll go over each migration strategy and its common use cases.

Retire

​Retire is the strategy we use for applications that we want to decommission or archive. This means that we can shut down the servers within that application stack. Here are some common use cases for the retire strategy:
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• There's no business value in retaining the application or moving it to the cloud.
• We want to eliminate the cost of maintaining and hosting the application.
• We want to reduce the security risks of operating an application that uses an operating system (OS) version or components that are no longer supported.
• We might want to retire applications based on their performance, such as those that have an average CPU and memory usage below 5 percent, which we call zombie applications. We might also retire some applications that have an average CPU and memory usage between 5 and 20 percent over a period of 90 days, known as idle applications. To identify zombie and idle applications, we can use the utilization and performance data from our discovery tool.
• Finally, if there has been no inbound connection to the application for the last 90 days, we might consider retiring it.

Retain

If you've got apps that you're not quite ready to migrate or that you want to keep in your source environment, the Retain strategy is your go-to. You might decide to migrate these apps at a later time, but for now, you want to keep them right where they are.

Here are some common scenarios where the Retain strategy is a good choice:
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• Security and compliance: If you need to comply with data residency requirements, you might want to keep certain apps in your source environment.
• High risk: If an app is particularly complex or has a lot of dependencies, you might want to keep it in your source environment until you can make a detailed migration plan.
• Dependencies: If an app depends on other apps that need to be migrated first, you might want to retain it until those other apps are in the cloud.
• Recently upgraded: If you just invested in upgrading your current system, you might want to wait until the next technical refresh to migrate the app.
• No business value to migrate: For apps with only a few internal users, it might not make sense to migrate them to the cloud.
• Plans to migrate to software as a service (SaaS): If you're planning to move to a vendor-based SaaS solution, you might want to keep an app in your source environment until the SaaS version is available.
• Unresolved physical dependencies: If an app is dependent on specialized hardware that doesn't have a cloud equivalent, such as machines in a manufacturing plant, you might want to retain it.
• Mainframe or mid-range apps and non-x86 Unix apps: These apps require careful assessment and planning before migrating to the cloud. Examples include IBM AS/400 and Oracle Solaris.
• Performance: If you want to keep zombie or idle apps in your source environment based on their performance, the Retain strategy is a good choice.

Rehost

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Rehosting your applications into the Cloud using this strategy is also called “lift and shift”. It means moving your application stack from your source environment to the Cloud without making any changes to the application itself. This means that you can quickly migrate your applications from on-premises or other cloud platforms to the Cloud, without worrying about compatibility or performance disruptions.

With rehosting, you can migrate a large number of machines, including physical, virtual, or other cloud platforms, to the Cloud without downtime or long cutover windows. This helps minimize disruption to your business and your customers. The length of downtime depends on your cutover strategy.

The rehosting strategy lets you scale your applications without making any cloud optimizations, which means you don't have to spend time or money making changes to your applications before migration. Once your applications are running in the cloud, you can optimize or re-architect them more easily and integrate them with other cloud services.
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With regards to AWS Cloud, you can make the migration process even smoother by automating the rehosting process using services such as:

• AWS Application Migration Service
• AWS Cloud Migration Factory Solution​

Relocate

If you are looking to transfer a large number of servers or instances from your on-premises platform to a cloud version of the platform, then the relocate strategy could be the right choice for you. With this strategy, you can move one or more applications to a different virtual private cloud (VPC), AWS region or AWS account. For instance, you can transfer servers in bulk from VMware software-defined data centre (SSDC) to VMware Cloud on AWS, or move an Amazon Relational Database Service (Amazon RDS) DB instance to another VPC or AWS account.

The relocate strategy is great because you don't have to buy new hardware, rewrite applications, or modify your existing operation. During relocation, your application will keep serving users, which means you'll experience minimal disruption and downtime. In fact, it's the quickest way to migrate and operate your workload in the cloud because it won't affect the overall architecture of your application.

​Repurchase

Repurchasing your application is a migration strategy that involves replacing your existing on-premises application with a different version or product. This new application should offer more business value than the existing one, such as accessibility from anywhere, no infrastructure maintenance, and pay-as-you-go pricing models. This strategy can help reduce costs associated with maintenance, infrastructure, and licensing.

Here are some common use cases for the repurchase migration strategy:

• Moving from traditional licenses to Software-as-a-Service (SaaS) to remove the burden of managing and maintaining infrastructure and reduce licensing issues.
• Upgrading to the latest version or third-party equivalent of your existing on-premises application to leverage new features, integrate with cloud services, and scale the application more easily.
• Replacing a custom application by repurchasing a vendor-based SaaS or cloud-based application to avoid recoding and re-architecting the custom application.

Before purchasing the new application, you should assess it based on your business requirements, particularly security and compliance. After purchasing the new application, here are the next steps:
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• Training your team and users on the new system
• Migrating your data to the newly purchased application
• Integrating the application into your authentication services, such as Microsoft Active Directory, to centralize authentication
• Configuring networking to help secure communication between the purchased application, your users, and your infrastructure

Typically, the application vendor assists with these activities for a smooth transition. 

Replatform

Replatforming, also known as lift, tinker, and shift or lift and reshape, is a migration strategy where you move your application to the cloud and introduce some level of optimization to operate it more efficiently, reduce costs, or take advantage of cloud capabilities. For instance, you can move a Microsoft SQL Server database to Amazon RDS for SQL Server.

With the replatform strategy, you can make minimal or extensive changes to your application, depending on your business goals and your target platform. Here are some common use cases for replatforming:
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• If you want to save time and reduce costs, you can move to a fully managed or serverless service in the AWS Cloud.
• To improve your security and compliance posture, you can upgrade your operating system to the latest version using the End-of-Support Migration Program (EMP) for Windows Server. This program lets you migrate your legacy Windows Server applications to the latest supported versions of Windows Server on AWS, without any code changes.
• You can also reduce costs by using AWS Graviton Processors, custom-built processors developed by AWS.
• If you want to cut costs by moving from a Microsoft Windows operating system to a Linux operating system, you can port your .NET Framework applications to .NET Core, which can run on a Linux operating system. You can use the Porting Assistant for .NET analysis tool to help you with this.
• You can also improve performance by migrating virtual machines to containers, without making any code changes. By using the AWS App2Container migration tool, you can modernize your .NET and Java applications into containerized applications.

​The replatform strategy allows you to keep your legacy application running without compromising security and compliance. It reduces costs and improves performance by migrating to a managed or serverless service, moving virtual machines to containers, and avoiding licensing expenses.

Refactor or Re-architect

Refactoring or re-architecting is a cloud migration strategy that involves moving an application to the cloud and making changes to its architecture to take full advantage of cloud-native features. This is done to improve agility, performance, and scalability, and is often driven by business demands to scale, release products and features faster, and reduce costs.

Here are some common use cases for the refactor migration strategy:
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• Your legacy mainframe application can no longer meet the demands of the business due to its limitations or is too expensive to maintain.
• You have a monolithic application that is slowing down product delivery and cannot keep up with customer needs and demands.
• You have a legacy application that nobody knows how to maintain, or the source code is not available.
• The application is difficult to test, or test coverage is low, which affects the quality and delivery of new features and fixes. Redesigning the application for the cloud can help increase test coverage and integrate automated testing tools.
• For security and compliance reasons, you might need to move a database to the cloud, but need to extract some tables (such as customer information, patient, or patient diagnosis tables) and keep those tables on premises. In this scenario, you will need to refactor your database to separate the tables that will be migrated from those that will be kept on premises.

By refactoring your application, you can take advantage of cloud-native features to improve performance, scalability, and agility. This strategy is particularly useful when your legacy application can no longer meet your business needs or is too costly to maintain. 

Summary

Cloud migration is a complex process that requires careful planning and consideration of various factors. As discussed in this article, there are several strategies that organizations can use to migrate their applications to the cloud, including rehost, refactor, repurchase, and retire. Each strategy has its own benefits and drawbacks, and the choice of strategy will depend on the specific needs of the organization.

While the benefits of cloud migration are many, including improved scalability, agility, and cost savings, it's important to approach the process with caution and to take a strategic approach. A successful cloud migration requires a clear understanding of the business goals and requirements, as well as careful consideration of security, compliance, and data protection.
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Organizations that are considering a cloud migration should seek guidance from experienced cloud migration specialists and take advantage of the many tools and resources that are available to help simplify the process. With careful planning and the right strategy, cloud migration can be a powerful tool for driving innovation, improving efficiency, and delivering real value to the organization and its customers.