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Cloud Migration Approach at a Glance

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Now is the era of cloud, and almost every SMB or Enterprises are trying to get advantages of IaaS, PaaS, and SaaS offerings by major cloud service providers like Azure, AWS, Alibaba Cloud, Google Cloud, IBM Cloud, Oracle (OCI) cloud.

For a fresh start, cloud is a superb choice as building cloud infrastructure is fast, cost-effective (no upfront cost as compared to on-premise DCs, and fewer management hiccups. Cloud is now becoming a primary choice for most of Sandbox, development, or validation environments.

But the challenge comes when it is required to migrate existing IT/Application infrastructure from on-premise to cloud or cloud to cloud. Cloud Migration involves several components and exercises to make it happen successfully. As public cloud usage increasing worldwide; there are lots of tools available for migration either provided by a cloud provider or third-party tools designed for specific cloud migration requirements. Even after that, for successful cloud migration, systematic planning is required, and it includes multiple phases technically.

For IaaS, PaaS, and SaaS platforms, different migration methodologies are adopted, but this article emphasizes on IaaS based migration scenarios as still, most of the migration scenarios are IaaS based.

For successful cloud migration, we can segregate the whole process into multiple phases. Typically the entire process flows like shown in the below diagram:

Assessment Phase: This is the most crucial step to ensure existing IT infrastructure and Application components.

A. Assessment of suitable cloud as per requirement, cost, performance, and services or feature-wise.

B. Inventory is needed to be assessed for cloud compatible workloads, and decisions are made against each inventory server/application.

C. In this phase, based on server and application it is evaluated which servers are candidate for As-Is Migration (P2V or V2V) (Some people call it as Lift & Shift as well, but it is more specific to DC to DC Migrations) on cloud and which servers need a new build strategy due to incompatibility with cloud platform support.

D. Apart from this, one should identify against each server that what kind of instance type will be required on a specific cloud.

Planning Phase: The planning phase holds equal importance as the assessment phase. To set up cloud infrastructure adequately and securely, the success of complete migration depends on this phase.

A. This phase includes designing of high-level design document (HLD), low-level design document (LLD) where cloud infrastructure is planned, and all components like nomenclature, Network, Security, compute and storage are taken care of based on existing infrastructure which is needed to be migrated.

B. A bill of materials/quantities (BOM or BOQ) is prepared in this phase to have a fair understanding and agreement about cloud components required and their cost estimation.

C. Identification/selection of required Migration Tools based on servers, Applications, and DB types is also planned in this phase. What IT-infrastructure and security are needed to set up migration tools are outlined in detail. In most of the cases, tools provided by cloud provider works well like Azure Migrate and Azure Site Recovery by Azure, Server Migration Services by Amazon or P2V tool and DTS services by Alibaba cloud, etc. But in some specific server, Application or DB scenarios, it needs to plan for third-party tools like Platespin-Migrate, Double-Take, AppZero, etc.

D. Planning of Move Groups (for phase-wise migration) is required to ensure a seamless migration as per requirement, application grouping, and agreed downtimes. Move Groups are needed to be formed as per different environments like development, Training, Validation.

Execution Phase: In this phase, actual implementation and migration happen as per planning done and according to the schedule agreed in Move Groups. The following are things that happen in this phase:

A. Cloud Foundation: In this step, selected cloud account/accounts are prepared as per agreed architecture in HLD and LLDs in the planning phase. It includes setting up VNets/VPC, Subnets, Resource groups, storage accounts or buckets, Security groups, Firewall appliances, WAF and other required security components, etc.

B. IT Infrastructure setup: In this phase, essential and required infrastructure is setup like Express-Route/Direct Connect, Active Directory infra, DNS/DHCP, Security, etc.

C. Setting up Migration tools: In this phase, the required IT-infrastructure is built-in on-premise DC and on Cloud as per the tool’s requirements.

D. Pilot run and validations: once migration tools are set up, a pilot run is required to see the functionality is as expected, or there are any hiccups due to any configuration, network, or security.

E. Migration: As per move-group and schedule, in this phase migration process is started. Migration process mostly divided in 3 following parts:


i) Initial Sync
ii) Incremental Sync
iii) Final Sync & Cutover

But these can differ from the specific scenario and used the migration tool. After final sync, cut-over tasks are vital. In cut-over tasks, moved workloads on the cloud are configured, and actions are taken on source servers (Stop or shutdown) so that there will be no conflict in between migrated workloads with the previous infrastructure.

Validation and Acceptance: Once workloads are migrated to cloud infrastructure, a validation exercise is conducted, which includes:

A. Server and Application Validation:  After successful cut-over migration team needs to check whether migrated server/Application/DB is started and functioning correctly or not. If there is any hiccup and cannot be corrected within acceptable timelines, it can call Rollback as well.

B. UAT exercise from Application or DB owners: Once checks have passed from the migration team, workloads must be tested through actual Application and DB owners.

C. Handover of migrated workloads to business: If everything is fine in migrated workloads on cloud it has to be handed over to business for resuming their regular operation.

Post Migration Tasks: Once Migrations are successful and business is moved to the cloud, there is still some important task which is needed to be taken care of. It includes:

A. Clean up and Decommissioning activities: All temporary or not required components must be removed from both source and Destination (Cloud) infrastructure. Physical or virtual servers that are migrated from source infrastructure to cloud must be decommissioned from source infrastructure to avoid any ambiguity in the future.

B. Support for Cloud Infrastructure: After the migration support team (BAU) needs to take charge of migrated infrastructure on the cloud to manage the seamless operation.

All the phases and steps mentioned above if used for cloud migration, can ensure a quick, successful, and seamless migration to the cloud. As things got documented in the assessment and planning phases, it helps admin and support teams further to manage cloud infrastructure efficiently.

Hemant Kulshreshtha
Hemant Kulshreshtha
Working in Paytm as AGM. 16+ years of experience with vast exposure to Cloud, IT infrastructure management and data center/Cloud migration/consolidation. Domain expertise on Cloud platforms (MS Azure, AWS, Alibaba Cloud), data centers, converged and hyper-converged technologies. Having extensive subject matter expertise on IT Infrastructure Architecting and Cloud/Datacenter Management.

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