A Guide to Cloud Migration Strategies

Cloud migration is no longer just a buzzword — it's a necessity for businesses aiming for digital transformation or updating outdated software systems. Shifting from on-premise to the cloud might seem overwhelming at first; it’s a complex process that takes meaningful time and consistency. An important key to success is to hone in on a migration strategy that makes sense for an organization and its infrastructure. In this article, we'll break down cloud migration and highlight some practical strategies to tackle it head-on. While there are six distinct strategies, we’re going to focus on two that we feel provide the most value: Rehosting and Replatforming.

Understanding Cloud Migration

Cloud migration, at its very essence, is about the transition. It's the journey of moving software and entire computing frameworks, whether that means in terms of design (logically) or actual hardware (physically), to a cloud-based infrastructure. Each organization's journey is unique; the scope and depth of this shift are largely determined by its specific operational demands, legacy systems, and long-term vision. 

On one hand, the cloud provides a massive lever for scaling and performance. However, it can also introduce security problems, complexity, and extreme cost if not managed carefully. Diving headfirst into the cloud without a strategic roadmap can lead to security vulnerabilities, a complex pile of technical debt, and budget overruns that far outweigh the benefits. It’s important to have a clear understanding of the existing infrastructure, stakeholder agreement, and a reasonable definition of “done”.

Types of Cloud Migration

The journey to the cloud is not one-size-fits-all. Depending on an organization's existing infrastructure, goals, and constraints, there are several migration strategies to consider. Among the most recognized are the 6 R's of cloud migration, each offering its own approach to the transition:

1. Rehosting: Often referred to as "lift-and-shift", rehosting involves moving applications and data directly to the cloud without making any modifications. It's like picking up a plant from one pot and placing it in another. This method is typically faster and requires less upfront investment. However, while it does get you to the cloud quickly, it may not allow you to harness the full array of cloud-native features and optimizations.

2. Replatforming: This strategy is about making minor optimizations before migrating, ensuring the application can capitalize on the cloud's benefits. It's akin to changing a car's tires before a long trip - the vehicle remains largely the same, but the journey becomes smoother. Replatforming might involve tweaks like adjusting the database to be more cloud-compatible.

3. Repurchasing: As the name suggests, this strategy involves switching to different products or services. A common example is moving from a traditional CRM to a cloud-based one like Salesforce. This approach means saying goodbye to legacy systems in favor of cloud-ready solutions.

4. Refactoring: Here, the migration is all about re-architecting and redeveloping an application to leverage cloud-native features. While this approach demands significant effort and resources, the payoffs in terms of performance, scalability, and feature-set can be substantial.

5. Retiring: During a cloud migration assessment, you might discover some of your IT assets are redundant or seldom used. Instead of migrating them, it might be more economical and efficient to simply retire them. This strategy is about decluttering and ensuring only value-driven applications make the transition.

6. Retaining: Not everything needs to move to the cloud, at least not immediately. Some applications might stay in the on-premises data center due to regulatory concerns, technical constraints, or strategic reasons. Retaining is about acknowledging that some systems are best left where they are, at least for the time being.

While each strategy offers specific benefits depending on context, the primary focus here will be on how organizations can take advantage of Rehosting and Replatforming using containers and PaaS.

Preparing for Cloud Migration

Once a cloud migration is on the roadmap, it’s time to start preparing. Regardless of the chosen migration strategy, preparation is essential to helping increase the chances of a successful migration.

1. Cloud Readiness Assessment: The foundational step to any migration process is assessing an organization's readiness for the move. This involves taking stock of the existing infrastructure, evaluating the technical and business aspects, and identifying any potential roadblocks or challenges. It's about asking the right questions: Can the current systems and processes adapt to the cloud? Are there specific legacy components that might not be compatible? These assessments help in streamlining the migration process and avoiding costly oversights.

2. Aligning with Business Objectives: It's crucial to have a clear understanding of what an organization aims to achieve with the migration. This might range from operational efficiency and scalability to entering new markets or serving customers better. Having clarity on these objectives will guide the migration strategy, ensuring alignment of technology investments with business outcomes.

3. Reviewing Obligations: Before making the move, it's imperative to ensure that hosting on a cloud platform won't breach any Service Level Agreements (SLAs) or contract obligations  with existing customers. This may involve revisiting contracts, engaging in discussions, or even renegotiating terms.

4. Goal Setting: Setting goals for a cloud migration should be pragmatic. While overarching objectives like "reducing costs" are important, they lack specificity and can be too nebulous to act upon effectively. A better approach is to set quantifiable targets. Instead of a vague "improve performance," organizations should aim for something like: "reduce deployment times by 25%." This not only provides a clear metric to work towards but also offers multiple avenues to achieve the target.

5. Evaluating Cloud Service Providers: The cloud landscape is diverse, with several large companies like AWS, Azure, and GCP offering a diverse portfolio of services. There are also numerous Platform-as-a-Service (PaaS) providers that provide higher-level abstractions, enabling smaller teams to deploy complete application infrastructure that’s fully managed. It's essential to evaluate potential providers based on specific requirements, costs, and the features they offer. Organizations should consider factors like global reach, support services, integration capabilities, and scalability. Perhaps more importantly, they should consider the available engineering staff and their infrastructure acumen. Smaller teams without dedicated DevOps resources might do well to go with a more dedicated PaaS solution.

Once preparation is complete, it’s time to choose and implement a migration strategy.

Cloud Migration – Taking Advantage of Containerization

Each organization is unique, and there isn’t a one-size-fits-all approach. Each infrastructure environment will have its own unique configurations and challenges. However, with the ubiquitousness of containers as an application runtime platform, many organizations can take advantage of the relatively low effort needed to containerize their software applications. For migrations that emphasize speed and relatively little change, Rehosting while introducing containers is the best option. If an organization wants to offload some of the operational burden, Replatforming with containers onto a PaaS is the best option.

Lift and Shift (Rehosting): 

The 'lift and shift' cloud migration strategy is a popular approach for organizations looking to move their applications and data from on-premises infrastructure to the cloud. The primary advantage of this strategy is that it requires minimal changes to the existing applications, making it a relatively straightforward and cost-effective migration path. By applying some effort to containerize applications, an organization can make rehosting easier, while laying the groundwork for bigger architectural shifts in the future.

Containerization is a method of encapsulating an application along with its dependencies into a single, self-contained unit that can run anywhere. This technology, powered by platforms like Docker and Kubernetes, offers several advantages that align perfectly with the 'lift and shift' strategy.

Firstly, containerization ensures application portability. Since a container includes everything an application needs to run, it can be moved seamlessly between different environments - from a developer's workstation to a test environment, and finally to the cloud. This eliminates the common problem of discrepancies between environments, often summed up in the phrase "but it works on my machine".

Secondly, containers are lightweight and start quickly, which can significantly improve the resource efficiency and start times for cloud resources. Unlike virtual machines, which each require a full copy of an operating system, containers share the host system's OS kernel, making them much more resource-efficient. Organizations can run more containers on a given hardware than they can with VMs, leading to cost savings in the cloud.

Finally, containerization supports microservices architecture, a design approach where an application is broken down into small, loosely coupled services. This is particularly beneficial in a cloud environment, where these services can be scaled independently based on demand. While this may not be the initial goal of a 'lift and shift' migration, containerization provides the flexibility to gradually refactor monolithic applications into microservices post-migration, without any drastic changes required up front.

Improve and Move (Replatforming): 

Organizations that want to take advantage of the cloud, but don’t yet have the organizational knowledge to handle the technical demands and operational overhead can replatform their applications onto a Platform as a Service (PaaS). A PaaS will often provide a fully-featured runtime environment for containerized applications, including hands-off deployment automation.

Depending on the size or make up of a software engineering organization, there may be limited to no staff resources available that can provide design and implementation guidance on cloud infrastructure (DevOps). Developers want to be able to deploy their code, and a successful migration will hinge on whether or not the on-premise applications provide the same functionality to customers once they are in the cloud. Replatforming to PaaS offers the benefits of the cloud without the headaches.

PaaS providers will typically own the majority of the operational and administrative burden around managing infrastructure and security. Teams don’t have to spend critical cycles debating what the best geographic distribution of compute nodes is, or how to set up aggregated logging. A good PaaS will provide the right number of useful abstractions, allowing developers to choose the type of application they will be hosting and the amount of resources they’ll need per node. Another aspect of cloud computing that’s often difficult to implement correctly, autoscaling, is no longer an issue in a PaaS. The platform handles scaling to meet increased traffic demands automatically without user intervention.

Since most PaaS offer first-class container support, typically Docker, developers often just need to include a valid Dockerfile with their application code, and the PaaS will automatically handle deployments and environment management. The organization can wait to design and implement more complex CI/CD architecture at a later time.

As a software organization grows, it can lean on containers to further scale and expand its software infrastructure, but for the critical window of time during a migration, it makes sense to let developers focus on delivering their applications effectively in their new cloud environment without having to focus on building it too.

Post-Migration – Ensuring Success

After transitioning to the cloud, it’s just as important to undergo a rigorous assessment of the outcome as it was the design. As mentioned earlier, having a clear definition of done is critical to being able to understand what success actually looks like, and whether or not it was achieved.

The first question to address is whether the set objectives were met. In a cloud migration scenario, objectives aren't aspirations; they demand clear, quantifiable outcomes. Was the project executed in alignment with the set benchmarks and parameters? While there may be nuances, it's essential for organizations to measure success and identify areas that may require further refinement. 

There’s also a need for an economic evaluation. Are the costs aligning with the initial projections, or are there unforeseen costs that need addressing? Excessive budget overruns may impact the ability of an engineering organization to get leadership buy-in for future cloud migrations or expanded usage.

Finally, security remains a cornerstone of any cloud migration. Continuous checkpoints should be established to monitor and ensure compliance. It's vitally important to determine if the organization is still meeting its Service Level Agreements (SLAs) and other contractual obligations, especially pertaining to data governance and custody. This adherence not only reflects good planning but is also indicative of the organization's commitment to its customers.

Successful Cloud Migration Means Choosing the Right Strategy

Selecting the ideal cloud migration strategy will ultimately depend on the organization and its goals. It's not a one-size-fits-all decision. However, the utility of containers as a way to package applications to run anywhere shouldn’t be overlooked. By leaning on containerization and PaaS, organizations can significantly reduce the time and technical effort that a migration requires, while setting themselves up for future growth and scalability.

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