In 2020, the global public cloud market is expected to exceed $330 billion. On an average, about a third of a company’s IT budget goes into cloud computing. The top reason companies adopt cloud computing is to be able to provide data access from anywhere. When any individual or organization thinks about migrating to the cloud, they have three core models that they can choose from – Software-as-a-Service (SaaS), Platform-as-a-Service (PaaS) and Infrastructure-as-a-Service (IaaS). All these three models provide a layer of abstraction to the users building application systems and reduce the effort required to build the applications. The models are then billed as a utility, based on customer consumption and usage in a ‘pas-as-you-go’ or ‘pay-for-use’ model, depending on customer preferences and choices.
About a decade ago, SaaS was the most popular model around the world. However, with time, that has changed considerably. Today, PaaS is the most popular cloud service model as it serves as a one-stop-shop for users.
Before understanding the differences between IaaS, SaaS and PaaS, it is important to know what are the different layers in a cloud stack. A cloud stack generally has four layers:
- The infrastructure layer: Compute resources, networks, storage and security
- The application stack: The operating system, application server software, databases, middleware, programming frameworks and monitoring
- The application layer: The user interface, the authentication and authorization, the transactions and the dashboards
- The user layer: Login, execute transactions management
Once we know these layers, we can better understand the details about IaaS, PaaS, and SaaS; as well as the differences between them.
Infrastructure-as-a-Service (IaaS)
As is evident from the name itself, the Infrastructure-as-a-Service or IaaS provides the Infrastructure later of the stack. Popular examples for this model are the AWS (Amazon Web Services) EC2 Rackspace and Google Compute Engine (GCE). The IaaS gives users cloud-based alternatives to on-premise infrastructure. With this model, one can avoid having to invest in expensive on-site resources. When using the IaaS model, one can provision, either manually via consoles or automatedly via API and code, the infrastructure resources for compute instances, storage and data repositories, networks, security services and other fundamental utility services, for instance, backups. This model enables customers to build and implement their software, could be an operating system or a custom application system on the infrastructure. In the IaaS model, customers would be responsible for managing and controlling everything in the cloud stack from the operating system layer and above, including the operating systems, data, application stacks, databases, middleware, programming language frameworks, security, operations like monitoring, patching, etc. as well as governance.
Platform-as-a-Service (PaaS)
This model, again as the name suggests, provides the application stack layer to the customer. Popular examples include AWS Elastic Beanstalk, Microsoft Azure, Oracle, IBM, Pivotal Cloud Foundry, Red Hat OpenShift Container Platform, etc. This model provides a development and deployment environment, including the software development framework of operating systems development tools and programming interfaces, such as, .Net, Java and Python. In this model, customers also get access to database systems and business analytics. This model also offers features like scalability, high availability, multi-tenancy, etc. With PaaS, the customer responsibility is limited to building their cloud-based application systems, while the cloud service provider would be responsible for taking care of infrastructure, application stack and management layers of the stack.
Software-as-a-Service (SaaS)
With the SaaS model, the entire application is delivered as a service via a third party over the internet, to the user. Popular examples of this model include Google Apps, Salesforce, Dropbox, DocuSign, Slack, HubSpot, etc. When using the SaaS model, it is the service provider that takes care of all the infrastructure, application logic, application deployments and service delivery. In turn, it is the users have to manage customer parameters and user engagements.
Which service model to choose – IaaS, PaaS or SaaS?
Irrespective of which model is chosen, the main purpose of any cloud service model is to help users save money and avoid having to spend precious time & resources on purchasing requisite equipment and hosting everything they need on-premises. Not everything can be handed over to third-arty vendors to manage in the interest of data privacy and security.
When choosing between IaaS, PaaS and SaaS, always remember the three Cs –
- Communication
- Collaboration
- Cooperation
These are the three necessities for being able to smoothly carry out their operations. So, here’s a comparative study of IaaS, PaaS and SaaS:
Choosing the right service model
The first rule for choosing the right cloud service model is – “The business needs should always drive the technology purchase and not vice versa”.
This is why a lot of organizations end up going for hybrid cloud service models, so as to be able to meet their diverse needs and requirements, while also keeping some applications on in-house storage to keep up with the demands for data privacy and security.
Here are the main factors one needs to consider when making a choice between PaaS, SaaS and IaaS:
- For migrating a legacy application to the cloud: Analyze the customized programs for their suitability and consider the impact of retrofitting of existing architectures for integrating them with the new cloud services
- Determining suitability of applications: Some applications are just not suitable for being moved to the cloud. Doing so would need significant amount of investment for re-architecting legacy architectures and also to re-write the cloud native applications
- Building new services: When new services need to be built, they must be built on the cloud for optimally using the cloud models
- How much change can the organization take at a go: When undertaking organizational change management initiatives, they would generally need to be accompanied by resource training, new resource on-boarding, bringing in requisite consultants, etc. The entire operation would need to be planned and implemented, keeping the possible impact in mind
- Impact and accessory requirements of transition: When transitioning over to the cloud, take into consideration how the transition would need a new operations model to be created, as well as what additional tools and services would be needed along with the chosen model
Keeping these considerations in mind, one can make the right choice between IaaS, SaaS and PaaS.
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