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Sandip Das for AWS Heroes

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Complete Cloud Migration Guide

One simple question that everyone reading this article will definitely have is:

"What is Cloud Migration"?

So, just to clarify, Cloud migration is when a company moves some / all of its on-premises or data center or other cloud resources & capabilities such as data, applications, or any other IT resources/processes/workload into the target cloud.

In more simple words: Although Cloud migration usually refers to moving all tech resources from old/legacy on-prem/data center to the Cloud, Cloud migration also can be moving from one cloud to another Cloud e.g. From On-prem to AWS, from Google Cloud to AWS Cloud or AWS Cloud to Azure

Compare it like moving a smaller office workspace to a bigger office workspace (on-prem to the cloud) or maybe challenging office locations! (One cloud to another cloud)

Before jumping in-depth into Cloud migration, let's understand few key concepts:

Cloud: Cloud in technology space means, Cloud Computing! and Cloud computing is the delivery of computing services—including servers, storage, databases, networking, software, analytics, and intelligence—over the Internet to offer faster innovation, flexible resources, and economies of scale. We typically have to pay only for cloud services you use, helping lower our operating costs, run our infrastructure more efficiently, and scale as business needs change.

Data: In computing, Data is information that has been translated into a form that is efficient for movement or processing.

SLA: A service-level agreement (SLA) defines the level of service you expect from a vendor, laying out the metrics by which service is measured, as well as remedies or penalties should agreed-on service levels not be achieved. It is a critical component of any technology vendor contract.

Legacy Infra: In computing, hardware or software is considered "legacy" if it is outdated but still in use. Legacy products and processes are usually not as efficient or secure as more up-to-date solutions. Businesses stuck running legacy systems are in danger of falling behind their competitors; they also face an increased risk of data breaches.

Why do Companies/Businesses need to move to Cloud?

Running from an on-premise or single data center, have three biggest limitations i.e.

1) Scalability: Running from an on-premise or single data center has limited resources hence limited scaling capability, moving to the cloud gives virtually limitless resource options, so limitless scalability opportunity & as per need!

2) Single Point of Failure: Running from an on-premise or data center create another big issue, i.e. it creates a single point of failure, in cases of natural disaster, un-wanted power supply cut or maybe a strike, the reason could be anything and operations/work processing can get stopped, but with Cloud Computing, it completely eliminates single point of failure if configured properly and there is no such chance and often Cloud Providers give SLA as well for it's services.

3) Cost: The cost of maintaining infra on-premise, operations, maintenance is huge, Cloud gives the "Pay as You Go" model which gives flexibility to only for using what is needed and stops using when not needed, in that way saving cost as well as reservations models which can bring up to 70% or more discount.

While talking about Cloud and migration, we also need to know about Types of Cloud Computing, Cloud Service Models, and Cloud Deployment Models

Types of Cloud Computing

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  • Public Cloud: This is a publicly accessible framework where one can store data or use it as a virtual machine. This can be done either by programming or autonomously. Here individual does not have to invest time and effort in buying physical servers but can get started in no time. Public clouds are available to use on pay per approach basis. e.g. Amazon Web Services (AWS), Microsoft Azure, Google Cloud Platform (GCP), Alibaba Cloud, IBM Cloud, and Oracle Cloud.
  • Private Cloud: If one needs to have a cloud exclusively for the organization then a private cloud is the best option. Along with the flexibility it provides one can opt for a data center on the premises for security and compliance needs. A dedicated professional is required to manage the private cloud framework. e.g. Hewlett Packard Enterprise (HPE), Dell, IBM, Oracle, and some familiar names from the public cloud provider space, including AWS, Google, and Microsoft.
  • Hybrid Cloud: Hybrid is a combination of public and private clouds. For certain business needs who can benefit from the combination are the ones who use a hybrid cloud.

Cloud Service Models

Cloud Migration Models

  • IaaS (Infrastructure as a Service): IaaS contains the basic building blocks for cloud IT. It typically provides access to networking features, computers (virtual or on dedicated hardware), and data storage space. IaaS gives you the highest level of flexibility and management control over your IT resources. It is most similar to the existing IT resources with which many IT departments and developers are familiar.
  • PaaS (Platform as a service): PaaS removes the need for you to manage underlying infrastructure (usually hardware and operating systems), and allows you to focus on the deployment and management of your applications. This helps you be more efficient as you don’t need to worry about resource procurement, capacity planning, software maintenance, patching, or any of the other undifferentiated heavy lifting involved in running your application.
  • SaaS (Software as a Service): SaaS provides you with a complete product that is run and managed by the service provider. In most cases, people referring to SaaS are referring to end-user applications (such as web-based email). With a SaaS offering, you don’t have to think about how the service is maintained or how the underlying infrastructure is managed. You only need to think about how you will use that particular software.

Cloud Deployment Models

Cloud Deployment Model

  • Cloud: A cloud-based application is fully deployed in the cloud and all parts of the application run in the cloud. Applications in the cloud have either been created in the cloud or have been migrated from an existing infrastructure to take advantage of the benefits of cloud computing. Cloud-based applications can be built on low-level infrastructure pieces or can use higher-level services that provide abstraction from the management, architecting, and scaling requirements of core infrastructure.
  • On-premises: Deploying resources on-premises, using virtualization and resource management tools, is sometimes called “private cloud”. On-premises deployment does not provide many of the benefits of cloud computing but is sometimes sought for its ability to provide dedicated resources. In most cases, this deployment model is the same as legacy IT infrastructure while using application management and virtualization technologies to try and increase resource utilization.
  • Hybrid: A hybrid deployment is a way to connect infrastructure and applications between cloud-based resources and existing resources that are not located in the cloud. The most common method of hybrid deployment is between the cloud and existing on-premises infrastructure to extend, and grow, an organization's infrastructure into the cloud while connecting cloud resources to internal system

Now, that we have covered key concepts of cloud and pre-requisite knowledge, let's learn about the step by step migration flow:

Step 1: Cloud Assessment:

The very first thing we must do is the below assessments and document everything!

Asses Cost:

We have to do below cost assessment and estimate the total cost of migration to make sure it doesn't exceed the assigned budget

  • The cost of the team what working on the migration project
  • The cost of creating infrastructure
  • The cost of Cloud Service Provider (CSP)
  • The Cost of Data Transfer
  • Post-migration development & maintenance cost

Asses Architecture:

We have to below Architecture assessment before starting actual cloud migration

  • Create a list of existing infrastructure resources such as servers RAM, CPU, storage, firewall, Databases, etc any and all IT Infra Resources.
  • Create a list of expected resources that will need to be created in the remote Cloud Services Provider's platform, based on the existing list.
  • Find out the way to save Infrastructure costs and what possible options are available and select the best possible options as per business budget and needs.
  • Do a GAP analysis, to make a list of the things that need to be done before moving applications and data to the Cloud

Asses Security

Before moving to the cloud we have to consider below security assessments

  • List existing security policies, frameworks, business mandatory policies which need special considerations.
  • List how to achieve the above-existing infra requirements in the target cloud or how to improve it even further using available Cloud Service provider given tools
  • List all the relevant Security options such as how to use them, are they incur the extra cost or are free of cost, how effective it is, etc

Step 2: Create Proof of Concept (POC):

Before starting actual full-scale migration, there has to be a proof of concepts with at least to see if we can move core services and/or core data or not, otherwise if start full-scale migration and find out that some or most important services are incompatible or unable to migrate due to any reason, that might cause havoc loss to the company/project, so it's best practice to create a PoC before processing further! consider the below points while creating the Pilot project:

  • After above three assessment it will be clear with which cloud provider the PoC need to be made i.e. with best possible less cost + more performance service + infrastructure + Best Security options
  • Plan to move core service and core data + service first rather than making it feature-rich, try to make a smaller app/data migration only, just to verify what you are expecting to work, are working at all for your app/service or not
  • Utilizing Cloud service provider provided tools to make this POC faster
  • Not just depend on the Cloud Service Provided Tools, but also have a look at the best possible open-source options

Step 3: Data Migration:

After PoC succeeds and is passed by top management, it's time to start the actual migration process and first, we will move the data:

Leverage Storage Options:

  • Select best possible storage option based on requirement + cost/budget + performance
  • While selecting the storage option, check for tools provided by the cloud service provider for the data migration
  • Check SLA, most of the service providers give SLA (Service Level Agreement) for their storage options, which might be a selection factor for mid/large/enterprise businesses.


After selecting the storage option, it's time to migrate actual data, and consider the below points:

  • Estimate the time it's going to take to complete the Data Migration, let the Operations team and management know, and get concept/approval
  • Make Schema / Format ready (if needed) in the remote cloud storage
  • Check if data pre-processing is needed, if so, do make processing is done before starting the migration process, e.g. for DB storage export data to CSV or JSON, and for an object at such as pic and doc file to zipping before moving, etc
  • Find out when application traffic is lowest, and notify customers that you are going to move data in that time, make an application in maintenance mode so that it doesn't create new data, then start the migration and keep the service unavailable during the migration time
  • After the data migration is done, don't just start using the new storage, instead use live data migration tools, which keep the old data storage and new data storage in sync until completely move to the new data storage option, and only move to the new data storage option till fully satisfied with the performance, security and stability of new storage, for this either use cloud service provided tool, or open sources data migration tools or just create your own custom solution!
  • If the data is too huge that it might not be wise to do a live migration, instead it will be better to use physical data move using cloud service provided paid data migration service, where they will come to you and copy all the data into some large drive and then take it back to their data center where they do copy data from the drive, it's faster and then you can do live migration for any new data.

Step 4: Application Migration:

There are 6 R’s of cloud migration define cloud migration strategies, which include — Rehost, Refactor, Revise, Rebuild, Replace, and Retiring.

  • Rehost - Rehosting can be thought of as "the same thing, but on cloud servers". Companies that choose this strategy will select an IaaS (Infrastructure-as-a-Service) provider and recreate their application architecture on that infrastructure. in short: moving applications to the cloud as-is.
  • Refactor - Companies that choose to refactor will reuse already existing code and frameworks, but run their applications on a PaaS (Platform-as-a-Service) provider's platform – instead of on IaaS, as in rehosting. in short: changing the app’s code to better support the cloud environment
  • Revise - This strategy involves partially rewriting or expanding the code base, then deploying it by either rehosting or refactoring. in short: moving applications to the cloud without major changes but taking advantage of the benefits of the cloud environment.
  • Rebuild - To "rebuild" means rewriting and re-architecting the application from the ground up on a PaaS provider's platform. This can be a labor-intensive process, but it also enables developers to take advantage of modern features from PaaS vendors. in short: rewrite the application from scratch.
  • Replace - Businesses can also opt to discard their old applications altogether and switch to already-built SaaS (Software-as-a-Service) applications from third-party vendors. in short: retire the application and replace it with a new cloud-native application
  • Retiring — After looking over everything in your environment, you’re likely to discover there are things you can remove without consequences, doing it can save money, improves security, and gives your people one less tool they have to learn to use. in short: Remove unnecessary resources

List of Available Cloud Migration Tools & Service

Leading Cloud service providers such as AWS, Azure, GCP gives us excellent migration tools as follows:

AWS cloud migration tools:

AWS Provides below Cloud Migration tools:

Microsoft Azure cloud migration tools

Azure provides below migrations tools/services

  • Azure Migrate — Microsoft’s built-in migration service serves as a central hub for tools, progress tracking, insights, and guidance to plan and successfully migrate to the cloud. Most other tools covered below are integrated into this central dashboard.
  • Azure Migrate: Server Assessment and Server Migration — These tools let you assess and migrate servers to Azure, including physical servers and VMware, Hyper-V, public cloud, and other VMs.
  • Data Migration Assistant — DMA helps locate compatibility issues that could derail your migration. It points out unsupported features, new features, and helps you plot a proper path for database migration.
  • Azure Database Migration Service — Migrate on-prem databases to Azure VMs.
  • Azure Data Box — Move large amounts of offline data to the Azure cloud.
  • Movere — This SaaS platform was acquired by Microsoft in 2019. It’s a discovery solution that increases business intelligence to see and control environments across.

GCP cloud migration tools

GCP Provides below migrations tools/services:

  • Transfer Service — Execute large-scale data transfers from online and on-premises sources to Google Cloud Storage.
  • Transfer Appliance — For offline bulk data migration, Transfer Appliance lets you securely capture, ship, and upload data using 100TB or 480TB models.
  • Migrate for Anthos — Migrate and modernize existing workloads to containers.
  • Migrate for Compute Engine — Get enterprise applications running in Google Cloud while data migrates in the background. Validate, run, and migrate applications without reworking them.
  • BigQuery Data Transfer Service — Let your analytics team set the foundation for a BigQuery data warehouse and schedule and automate data transfers from your SaaS applications.

Step 5: Leverage Cloud:

Finally, after migration over, remember migration is not just moving data and application to the cloud, don't forget your primary goal, which was to leverage full power, do below to harness it:


  • So set auto-scaling policies properly, don't overestimate and don't underestimate, set auto-scaling policies based on application need.
  • Over-provisioning costs more and under-provisioning costs clients, which can impact Companie's Goodwill, so either is not an option, do experiment scaling as much as possible with Cloud Service provided tools and as well as open-source tools, practice chaos engineering!
  • Look at Multi-Cloud, using containerization or function-based application running approach, we can separate codes(business logic) from Environment (OS/other dependencies), Cloud gives us awesome multi-cloud features, where we can leverage multi-cloud so that in case any outage in any cloud, there is another backup Cloud service provider ready to compensate that.


Cloud gives us wonderful automation options such as:

  • We can automate infrastructure creation/provision, maintenance, upgrade/downgrade, security, kind of everything via Infrastructure as code tools/services such as Terraform, CloudFormations etc, we should and must utilizing this awesome feature
  • Using Automation, migration from one cloud to another is also easy (in case don't use the property tools/service, instead use opensource options)
  • Using Automation tools, also help estimate better in cost calculation and lets us know what resources going to be created before creating it!
  • Even using automated CI/CD process, from source code to deployment all can happen automation or using less manual international, making release process much faster and smooth


The test will get even easier:

  • If we maintain infrastructure as code, we also can add automated test cases that will make cloud resource testing much easier
  • If we maintain the automated CI/CD Process in the cloud, we can do easily add test cases in source code and do run the test cases after build successes and after testing, if passed, then moving to staging/production
  • If during the test it failed, using a different Cloud feature we can notify the concerned team about the failure and as soon the fixes and done and codes pushed, the testing can happen automatically again

Step 6: Optimizations :

After all the above in place, it's time to do the below:


  • Monitor cost, do create budget and notification, as it's very easy to thing can go out of budget and hard to manage, so have to make sure it's always under control and keep it under control.
  • Monitor Security, do make sure its least privileged approach is followed, monitor each and every access using cloud service proved tools, set alert for possible breaches, make sure strict policies are in place and set an alert if anyone tries to deviate anything, should trigger alert and automation there to rectify it.
  • Monitor performance, do monitor performance of each and every resources, check if any improvements if not, and do as needed
  • Monitor usage pattern, create separate usage profiles, like many hours running, when the load is high or less, how much usage happening, over the month, quarter, year etc, it will use in the next stage


After motioning and tethering enough data :

  • Improve based on fact, based on monitoring data, find out what resources needs improvements/upgrade/downgrade, etc
  • Look for Cost Saving opportunities, by profiling data and requirements, we can predict the next usage pattern and by leveraging this knowledge we can save cost by either by doing reservations or purchasing savings plans provided by Cloud Service proves, for this we need how much to reserve and monitoring gives us that data.
  • Improve security, by looking monitoring data & analyzing the data, find out anomalies, possible breaches, and find opportunities to improve it
  • Remove unnecessary resources, based on monitoring remove the resources which is unnecessary and not getting used at all

Migrations Challenges:

Duration: Although with help of modern tools and services migration takes less time, but in the case of legacy systems it takes a lot of time.

Complexity: Mapping existing systems and requirements to Cloud is no easy task and often it's very easy to get things more complicated, need very talented/experienced resource to handle the migration

Huge Bills: If not monitored and managed properly, cloud costs can go out of the hands

Make Management Understand: Let's agree, Cloud is complicated for non-teach / non-trained persons, management often doesn't know why and what, it's tough to make them understand what is needed and why is needed and its impact on laymen understandable way.

Human Resource: Probably the most important is this, Cloud migration need experienced knowledge hence experienced professional needed for do asses existing infra, plan the architecture of the cloud and not to mention actually implementing the infra/automate it and do the migration. For this we need, Cloud Architect, DevOps Engineers, Operations Engineer, etc, and since Cloud professionals are in demand, finding the right person is challenging.


Even though at a glance it looks like Cloud migration is moving resources to Cloud is just moving on-prem to Cloud, but it requires a lot of considerations before actually starting migrations and post migrations manage it.

Hope the information I have tried to provide will be beneficial for many others and if you really loved this article, do like this article, share it with others, and comment on what is yours thought about this article.

About the Author:

Sandip Das works as a Sr. Cloud Solutions Architect & DevOps Engineer for multiple tech product companies/start-ups, have AWS DevOps Engineer Professional certification, also holding the title of "AWS Container Hero",

He is always in "keep on learning" mode, enjoys sharing knowledge with others, and currently holds 5 AWS Certifications. Sandip finds blogging as a great way to share knowledge: he writes articles on Linkedin about Cloud, DevOps, Programming, and more. He also creates video tutorials on his YouTube channel.

Top comments (1)

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Sandy Lewis

Wow very detailed information. If anyone want to know more cloud migration strategies, visit our website.