Information gathered during the inventory collection is used to build a list of requirements for each application.

Requirements Gathering

For each application, the requirements can be organized by design attributes, that includes, but is not limited to, the following:

  • Scalability - The ability for a system to continue providing the same level of performance or functionality when there is a change in utilization.

    • For example, an application architect has a requirement that the underlying infrastructure must be able to scale out dynamically if there is an increase in traffic load. This may translate to a scalability requirement where the underlying infrastructure must be able to add or remove a compute capacity within an acceptable time frame.

  • Availability - The ability for a system to continuously operate and function for an extended time without interruption.

    • For example, the Virtual Machine workloads has a requirement that the underlying virtual infrastructure can provide an SLA of 99% uptime per month for management. This may translate to an availability requirement of a VMware Cloud SDDC having a minimum of 99% uptime or greater.

  • Recoverability - The ability for a system to recover from a disaster or a failure.

    • For example, an application architect requires the data for the application cannot tolerate data loss for more than 2hrs. This may translate to a recoverability requirement where the date for the Recovery Point Objective (RPO) must not exceed 2hrs.

  • Manageability - The measure of how easily a system can be deployed, configured, and controlled.

    • For example, an organization has a requirement to provide end users with a solution that enables self-service workload provisioning with governance. This may translate to an evaluation of a cloud management platform (CMP) that integrates with a VMware Cloud SDDC.


Tools such as VMware Aria Automation Cloud and other third-party solutions that are supported with VMware Cloud can be used as a CMP.

  • Performance: the measure of how well a system accomplishes a given task.

    • For example, the application has a requirement to deliver at least 100 concurrent requests per minute to satisfy its service SLA. This will translate to the supporting virtual infrastructure provisioned with the necessary compute, network, and storage resources to meet the application requirement.

The finalized list of requirements must be validated with the appropriate stakeholders within the organization through workshops or interviews before continuing with the assessment.

VMware Cloud Migration Strategy

With clear requirements and a holistic understanding of the application inventory, an organization can now determine an appropriate migration strategy for each application based on the needs of the business.

Figure 1. Common Migration Strategies

Common Migration Strategies
  • Refactor / Build involves changing the application at the source code level. Typically, applications are re-written to take advantage of cloud microservices architecture and to incorporate new services such as IoT, machine learning, and others

  • Replatform involves changing the operating system, such as going from Windows to Linux, modifying the application middleware, such as going from a self-managed database to a cloud provider managed database or from a virtual machine to a container image

  • Rehost / Migrate involves either changing the hypervisor. (e.g., migrate applications from one virtualized environment to another) which is known as Rehost or moving an application without changing the underlying hypervisor or application at a source code level (e.g., migrate VMs from one virtualized environment to another without requiring changes) which is known as Relocate

  • Retain means leaving workloads and/or applications in a private cloud environment

  • Retire means decommissioning workloads and/or applications, which can involve eliminating them altogether or converting to SaaS

It is important to understand that application modernization is not one specific approach but can be a combination of approaches. A common strategy that organizations have adopted to help accelerate their application modernization journey is first to migrate their existing workloads to a VMware Cloud SDDC and then modernize the underlying application.

Certain migration strategies, such as Refactor and Replatform, provide an opportunity for an organization to modernize their applications after migrating to VMware Cloud. The speed at which a modernization project is executed largely depends on an organization’s business outcomes and timelines.

Organizations will be most successful in achieving their application modernization (app modernization) goals by leveraging a Migrate and Modernize strategy. By migrating existing Virtual Machine workloads to VMware Cloud, organizations will now have a modern infrastructure platform. Organizations will now be able to focus on their app modernization efforts.

Migration Network Connectivity

For each batch of workloads to be migrated, the migration path and method must be determined.

There are various network connectivity options to create a migration path from an on-premises environment to a VMware Cloud SDDC, such as using a VPN or setting up a direct, private connection. Analyzing findings from the infrastructure assessment would help identify feasible network connectivity options for an organization’s specific business needs and requirements.


VMware HCX can be used to provide a private, secure connection and migrate workloads between an on-premises environment and a VMware Cloud based SDDC. VMware HCX also provides different migration methods, such as cold migration, bulk migration, and live migration.

Migration Wave Planning

Wave planning is the process of grouping workloads that will be migrated concurrently based on business critically and application dependencies to help create a high-level migration schedule. Workloads can be migrated based on the application SLAs, for example non-mission critical workloads can be migrated initially.

It is also critical to understand the different types of migration methods and an organization should select the one based on the needs of the business. For example, a Dev/Test workload which can afford downtime during the evenings, a production workload that cannot afford any downtime, and a staging workload which can have minimal downtime when scheduled. From a migration execution standpoint, you would then select three different migration types as mentioned below for each of the respective workloads, maximizing the speed at which you can migrate the workloads and maintaining the application service level agreements (SLA).

There are different methods for migrating workloads such as hot, warm, and cold migration:

  • A hot migration is referred to as a live migration and is the most familiar to VMware administrators. It is a staged migration where the virtual machine stays powered on during the initial full synchronization and the subsequent delta sync, using the VMware vSphere® vMotion® feature.

  • A warm migration is a virtual machine that is actively running while it is being replicated to ensure minimal downtime. After the migration completes, you either start a manual or automated cutover to make the replicated virtual machine available on the cloud provider. Cutover is a process of powering on the virtual machines at the cloud provider site after the warm migration gets completed. This cutover operation includes a final sync and import of the migrated VM into a destination VMware Cloud SDDC.

  • A cold migration is a virtual machine that is in a powered-off state before starting the migration. Exporting and importing virtual machine images is another form of cold migration.

Migration waves should also incorporate the related application dependencies and network communication traffic to keep intra-application traffic within the same environment and limit traffic across an on-premises data center and/or a VMware Cloud based SDDC.

In addition to grouping by applications, isolated waves should be created for large or complex workloads, such as database virtual machines or virtual machines with a high data change rate. These workloads tend to require more network bandwidth for migration and could impact other migrations if performed concurrently.


VMware Aria Operations for Networks can be used to validate application dependencies and traffic flows. VMware HCX integrates with VMware Aria Operations for Networks can automatically create a VMware HCX Mobility Group which migrates pre-defined set of workloads based on a migration wave planning.

VMware Cloud Design

After a thorough assessment of the existing infrastructure and workloads, the results will guide an organization in creating a VMware Cloud SDDC using design decisions based on compute and storage sizing, service location selection, and network connectivity.

The requirements gathered during the assessment will guide the design decisions for all aspects of a VMware Cloud SDDC, such as compute and storage sizing, service location selection, and network connectivity.

Appropriate compute and storage sizing must be determined for the VMware Cloud SDDC include resources for management components and overhead as well as the expected growth of workloads when sizing the VMware Cloud environment.


VMware Cloud Sizer should be used to help an organization size the VMware Cloud based SDDC. The VMware Cloud Configuration Maximums document should also be referenced to ensure scalability of a VMware Cloud SDDC.

Service location for a VMware Cloud SDDC should be chosen depending on the requirements, such as the following:

  • Availability of services: not all VMware Cloud services are available in every region

  • User locations: depending on the business needs (i.e., market expansion, local security compliance) and application requirements (i.e., service feature availability, minimum latency for optimal performance), an organization’s service(s) may need to be in close proximity to their end users.

Network connectivity for a VMware Cloud SDDC depends on the business needs and requirements. If an organization decides to keep the on-premises environment and use VMware Cloud for bursting to meet unexpected demands or for disaster recovery of the on-premises environment, permanent network connectivity may be needed between the two environments. If an organization decides to decommission the on-premises environment, then only network connectivity for the migration will be needed. In addition to deciding on the longevity of a network connection, data on network utilization and application traffic flows collected during the assessment should be utilized to determine the type of network connectivity and the required bandwidth.

It is important to remember that a VMware Cloud SDDC design must meet all the identified requirements. A detailed example of how a VMware Cloud based SDDC can be designed to meet availability, recoverability, and scalability requirements is discussed in the next section: Designing for Scale, High Availability, and Recoverability.