What is Infrastructure as a Service (IaaS)?

IaaS is the most flexible category of cloud services
It provides maximum control for your cloud resources
The cloud provider is responsible for maintaining hardware, network connectivity, and physical security
You are responsible for operating system installation, configuration, maintenance, network configuration, database and storage configuration, etc.
IaaS allows you to rent hardware in a cloud data centre

Shared responsibility model

This applies to all cloud service types
IaaS places the largest share of responsibility on you
The cloud provider is responsible for maintaining physical infrastructure and internet access
You are responsible for installation, configuration, patching, updates, and security.

Scenarios

Some common scenarios where IaaS might make sense include:

Lift-and-shift migration: You’re standing up cloud resources similar to your on-prem datacenter, and then simply moving the things running on-prem to running on the IaaS infrastructure.
Testing and development: You have established configurations for development and test environments that you need to rapidly replicate. You can stand up or shut down the different environments rapidly with an IaaS structure while maintaining complete control.

Platform as a Service

What is Platform as a Service (PaaS)?

PaaS is a middle ground between infrastructure as a service (IaaS) and software as a service (SaaS)
Cloud provider maintains physical infrastructure, physical security, and internet connection
The cloud provider also maintains operating systems, middleware, development tools, and business intelligence services
Allows for a complete development environment without the need for infrastructure maintenance

Shared responsibility model

This applies to all cloud service types, including PaaS
Responsibility is split between the user and the cloud provider
Cloud provider maintains physical infrastructure and internet access
The cloud provider also maintains operating systems, databases, and development tools, similar to IT maintaining a domain-joined machine
Users may be responsible for networking settings, connectivity, network and application security, and directory infrastructure.

Some common scenarios where PaaS might make sense include:

Development framework: PaaS provides a framework that developers can build upon to develop or customize cloud-based applications. Similar to the way you create an Excel macro, PaaS lets developers create applications using built-in software components. Cloud features such as scalability, high availability, and multi-tenant capability are included, reducing the amount of coding that developers must do.
Analytics or business intelligence: Tools provided as a service with PaaS allow organizations to analyze and mine their data, finding insights and patterns and predicting outcomes to improve forecasting, product design decisions, investment returns, and other business decisions.

Software as a Service (SaaS)

SaaS is a cloud service model where you rent or use a fully developed application
Email, financial software, messaging applications, and connectivity software are examples of SaaS
It is the easiest cloud model to set up and requires minimal technical knowledge

Shared responsibility model

This applies to all cloud service types
In SaaS, the cloud provider has the most responsibility, and the user has the least
The user is responsible for data, devices, and users with access
The cloud provider is responsible for physical security, power, network connectivity, and application development and patching.

Some common scenarios for SaaS are: