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Rehosting AWS Cloud

Rehosting in AWS

Rehosting is one of the methods of migration when discussing implementing an existing application into AWS.  It is a complex platform and existing workloads may not be able to be ported over.  But as daunting as the proposition might seem, AWS does intend on providing a smooth and cost effective transition for development teams.

Moving an Existing Project

As explained in our article covering migration methods, rehosting (or “lift-and-shift”) is the process of moving applications or solutions from on-premises environments to the cloud with no modification or as little modification as possible.  This is usually to achieve certain business objectives, such as driving down operational costs or launching an application easier.  Through services like the AWS Application Migration Service, cloud migration can be made fairly affordable and data can be replicated in the background with minimal disruption to operations or performance.

AWS Cloud Rehosting Method

Why Consider Rehosting

Our team of AWS specialists are trained and have extensive experience with this model of migration.  Applications in the cloud are easier to optimize or re-architect to incorporate new functionality.  The cloud does offer a great range of visibility and flexibility with how architecture can be arranged to best suit operations optimally.

 

Cheaper Maintenance

This will be the primary reason any organization will consider rehosting their application or infrastructure to AWS, especially in the long term.  Infrastructure can be incredibly expensive to upkeep in a physical data center.  That said, it isn’t necessarily more expensive than keeping an application running in the cloud.  If maintenance costs can be reduced or halved by hosting in the cloud, migrating to the cloud should be considered as an option.  Changes will be minimal if any and the process can be made affordable.  Even if maintenance costs are already considerably low in a physical environment, the difference is still worth the migration.

 

Issues Within the Cloud

Sometimes, an organization already is situated in the cloud but is facing technical issues.  A hard reset could prove beneficial and is highly recommended.  This can be done especially quickly as the application is already adapted to the cloud and it’s just a matter of moving everything to an environment with all the same settings established as the old environment.

 

COTS Applications

Commercial off-the-shelf applications come pre-baked and with rigid designs, meaning making code changes to such applications is just not physically possible.  By copying the architectural design to the cloud, the application can then be reformatted to the new needs of the application.

 

Retiring Legacy Designs

Applications may require optimization because they implement a number of antiquated design aspects and will need to be modernized.  Rehosting will provide a good opportunity to move the application to an environment where steps for modernization are more visible and can be considered more easily.

As we continue to evaluate a particular application or solution, this is a topic that will need to be discussed internally as well.  This is an opportunity to gather inputs, reevaluate current tasks and how they will affect the ability to reach certain requirements during the migration, and modify these tasks to support at least three-quarters of the current application workload.  AWS will have tools to help build a proof of concept in a test environment to see how the application can improve or deteriorate as a result of the migration.  Every step of the way, we’ll be helping to calibrate, assess, and evaluate various services available to recreate everything.

Preparation

During this stage, clients will be working with our experts.  They will review the pre-confirmation app questionnaire the client has filled out and further interview the application owners to validate server inventory.  As they continue to evaluate the application, they will conduct the following:

    • Validation of the network and storage dependencies/requirements
    • Ensure high availability and disaster recovery (HA/DR) for data works
    • Put together a diagram of the application in the current state
    • Acquire server information and server groups
    • Add any missing server details
    • Prepares a map of the infrastructure applied to the target AWS instances

Execution

In preparation, the Application Migration Service agent is installed on the servers that plan to rehost.  Data replication is tracked for each server and the steps needed for migration are at this point fully automated.  Our specialists will need a running list of all dependencies and inbound/outbound network ports and access to generate all the balancer requirements, firewalls, subnets, and security groups at the AWS landing zone.  Meanwhile, the application’s QA team will need to prepare test scenarios to run the application through once the migration is done to check dependencies.

It’s important to have backup strategies derived before the migration to rollback in case of disasters mid-migration.  In short:

    • Create the cutover runbook document and validate it with stakeholders - everyone will want to know
    • Validate the Application Migration Service blueprint, tag information, Domain Name Service (DNS), and security groups
    • Obtain approval from stakeholders
    • Perform tests once the migration is complete.

After everything is complete, the owners will need to run some sanity checks or testing to make sure everything works according to the application’s requirements.

Download our 10-Step Cloud Migration ChecklistYou'll get direct access to our full-length guide on Google Docs. From here, you will be able to make a copy, download the content, and share it with your team.