Cloud Delivery Models

Cloud services are delivered by a specific and a pre-packaged combination of IT resources known as cloud delivery models offered by a cloud provider. A cloud delivery model is also considered as a cloud service delivery model. The common type of cloud delivery models which are widely accepted and established:

  • Infrastructure-as-a-service (IaaS)
  • Platform-as-a-service (PaaS)
  • Software-as-a-service (SaaS)

These three models are interrelated in terms of encompassing one-another and have their own sets of benefits that could serve the needs of various businesses.

Infrastructure-as-a-service (IaaS) – It is a complete IT environment, includes hardware, software, network, connectivity, operating systems, and other raw IT resources, comprised of infrastructure-centric IT resources that are managed and accessed through cloud service-based interfaces and tools. The IT resources, in the environment with IaaS, in contrast to traditional hosting are generally virtualised and packaged into bundles. These bundles further simplify up-front runtime scaling and customisation of the infrastructure.

The basic purpose of such environment is to provide cloud consumers with a high level of responsibility and control over its configuration and utilisation. Basically, it is a virtual provision of computing resources over the cloud. Different cloud providers offer different types and brands of IaaS based IT resources.

IaaS environment allows Businesses to opt for computing resources of their requirement without installing hardware on their premises.

Platform-as-a-service (PaaS) – It represents a pre-defined “ready-to-use” environment comprised of deployed and configured IT resources. It basically relies on the usage of a ready-made environment establishing a set of pre-packaged products and tools used to support the entire delivery lifecycle of custom application. This means the PaaS environment provides an ease to develop, test, and organise the different applications for businesses. The virtual runtime environment provided by PaaS gives a favourable position for developing and testing applications.

Businesses prefer to use and invest in PaaS environment to

  • Extend on-premise environments into the cloud for scalability and economic purposes.
  • Use the readymade environment to entirely substitute an on-premise environment.
  • Become a cloud provider and deploy its own cloud services for external consumers.

The entire resources offered by PaaS in the form of servers, storage, and networking are manageable by the company or cloud providers.

Software-as-a-service (SaaS) – It is used to make a reusable cloud service widely available to a range of cloud customers. The entire business existing around SaaS products can be leased and used for different purposes. It gives quick access to the cloud-based web application and other tasks like working on excel, word online, Email, ERP tools, etc. These applications run on the cloud and can be used on a paid subscription or for free with limited access. But a cloud consumer has limited administrative control over a SaaS implementation.

SaaS applications are also known as on-demand software and web-based software.

It does not require any installation in existing infrastructure and thus is cost-effective and works on a pay-as-you-go model. It also eliminates the need for installing applications on each computer with the maintenance and support taken over by the vendors.

It is often updated more frequently than the traditional software for factors like

  • The application is centrally hosted, so providers, not customers, decide an execution and update.
  • The application has a single configuration making development testing faster.
  • The vendor has access to all customer data, expediting design, and regression testing.  

Comparing Cloud Delivery Models

Comparison based on control levels.
Comparison based on activities carried out by cloud consumers and cloud providers. (The comparisons are taken from book titled ‘Cloud Computing – Concept, Technology, & Architecture’)

The Last Corner

SaaS is well suited for cloud-based software like email, CRM, and productive tools whereas IaaS is best for complete virtualization while PaaS is the best choice for a platform to develop and test software and applications. The choice of cloud delivery models is dependent on business requirements and needs.  

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