For on-site deployments the whole responsibility of over hardware, infrastructure, operating system runtime and the application is all on the shoulders of the owning organization.
When organization decides to make use of IaaS model, which is “Infrastructure as as Service” – the responsibility over hardware and infrastructure is transferred from the organization to the service provider. But the application owner still needs to manage operating systems, runtime and the application itself. The example of this deployment is utilizing Virtual Machines.
One step ahead is PaaS, which transfers even more responsibility and administrative overhead to the service provider. This time the management of the operating systems and runtime is transferred to the service provider. But the application owner still needs to manage the code of the application. Example of the PaaS offering is Azure Functions or App Service – solution that hosts web apps in Azure.
The highest level of responsibility left to the service provider is in the SaaS model. In that model the service provider takes over the responsibility over everything just like in IaaS and PaaS, but also – it manages the final code and maintenance of the software application. In this scenario, the customer only consumes the functionality of the application without any insight into the code or software development.
PaaS vs other models
PaaS can only be well described when compared to other models and how they approach resources and processes.
Software development in Azure PaaS offerings
In contrast to SaaS – in PaaS, application owner is responsible for software development and code maintenance. This means two things. One – the owning will only get the functionality which he develops by himself. Microsoft will not provide some off-the-shelf solutions to run in Paa+S model. Two – the personnel maintaining the code is managed by the owner. Microsoft does not provide any professional software development services, the development stays within the organization.
Storage in Azure PaaS offerings
For azure PAAS offerings, such as App Service or Function Apps you need to utilize a storage service such as multipurpose Azure Storage Account. This gives you unlimited storage with metered billing. Which means – you get as much storage as you utilize, as long as you pay monthly usage costs.
Hardware in PaaS offerings
Just as in IaaS – the responsibility over hardware is on the cloud provider. Organization utilizing public cloud does not require a data center. Yet, with PaaS – the operating system is also abstracted away from the application owner. This allows the compute power to scale automatically.