Cloud migration guidance

Deciding which applications should be deployed in a cloud environment can easily become a political, licensing and operational issue. The strong familiarity with existing environments, as well as an overenthusiastic appetite for cloud services, can drive applications in the wrong direction.

NHS and healthcare providers must carry out an assessment to the following defined characteristics of the workload which will dictate placement rules.

These characteristics will allow you to:

• define which applications cannot be deployed using cloud computing, when using a cloud-first approach
• identify the ideal candidates for cloud deployment, when you’re using a cloud-last approach
• prioritise the migration of your applications from an on-premises data centre

Workload migration attributes that have to be assessed in order to make your placement decisions include

NHS and healthcare organisations that are just getting started with cloud computing often want to begin with low-risk applications. Low-risk applications allow them to better absorb the impact of mistakes without jeopardising the entire cloud initiative. NHS and healthcare organisations can adopt a methodology for determining application risk scores, and then use those score values to make placement decisions.

This category includes the technical characteristics that you can use to determine the cloud readiness of an application. By assessing an application’s operating systems, licensing requirements, state-fulness/statelessness, and other attributes, you can determine if it is ready for cloud computing from a technical standpoint. In the context of a cloud migration, the technical fit determines whether an application can be migrated as is or whether it requires a certain amount of changes.

Not all of your applications deliver an equal impact within the NHS or healthcare organisation. Some will be vital to the business, while others will have a marginal role. Understanding the value of the applications will help prioritise the investments necessary to improve their technical fit. The more valuable your applications are, the more it will be pressed to realise the benefits of cloud computing, such as greater agility and scalability.

Supporting information

More information on workload assessments can be found in choosing a cloud migration strategy for applications.

NHS and healthcare cloud placement policy will help determine whether an existing application should be migrated to cloud computing. An application could migrate as is, or it may require some transformation to ensure compatibility or to maximise the benefits from the cloud model. If you opt for transformation. The NHS or healthcare organisation will need to carry out an assessment on how much transformation the organisation is willing to accept in relation to the expected return.

To help with this migration decision, the NHS will follow the Gartner 5R’s framework. This framework describes the principles, requirements and constraints that govern the selection of a migration strategy from five proposed alternatives: re-host, revise, rearchitect, rebuild or replace. As depicted in the diagram below, these alternatives require varying levels of investment to realise varying levels of cloud benefits (such as agility and scalability). Consequently, you will have to develop a ROI for your chosen migration strategy.

See the Choosing a cloud migration strategy for applications section What is a Workload Assessment?’

If you prioritise speed of migration (in the case of a data centre consolidation initiative), you’ll be better served by the “rehost” or “replace” alternatives. Conversely, if you are adopting cloud services to improve your application scalability and modernisation, you may want to prioritise “rearchitect” or “rebuild.”

Cloud computing is delivered at different tiers:

• IaaS, Infrastructure as a Service
• PaaS, Platform as a Service
• SaaS, Software as a Service
• FaaS, Function as a Service

Each of these tiers permits a different degree of benefits, choice and control. You must define how you intend to prioritise the choice of cloud tier as part of your placement decision using the workload placement policy. For example, your choice can be governed by the following approaches:

Many organisations choose to adopt a SaaS-first approach because SaaS delivers most of the benefits of cloud computing with the lowest barrier to adoption. However, not all applications exist as SaaS. The SaaS model shifts the majority of the control and risk to the provider, which some NHS and healthcare organisations may not be willing to accept. Custom applications require a platform that is capable of running the NHS or healthcare's organisations application or code. PaaS is the default cloud computing choice for application platforms. Older applications may not be compatible with existing PaaS offerings; thus, NHS and healthcare organisations may be forced to consume cloud computing at the IaaS tier. This is an example of how you can define a priority order between cloud tiers, based on the desired degree of benefits and control.

There is a correlation between the chosen migration strategy and the target cloud tier. The “rehost” and “revise” strategies are probably going to be executed at the IaaS tier, “rearchitect” and “rebuild” on PaaS, and “replace” on SaaS. This rule is not strict, but these are the outcomes that are observed most frequently. In this case, the chosen migration strategy dictates the preferred cloud tier. These two approaches are not mutually exclusive and can be used in conjunction. For example, you may opt for a “rearchitect” strategy (which aligns to PaaS), only to realise that there are no PaaS platforms that meet your regulatory requirements. In this case, you’d be forced to move down to IaaS. Similarly, you may want to replace your ERP system with a SaaS alternative, but can’t find a vendor that accommodates the customisations of your commercial off-the-shelf (COTS) application. In this case, you’d also be forced to “rehost” your application in an IaaS environment.