Cloud computing and its basics

Cloud computing is a type of computing that provides multitenant or dedicated computing resources such as compute, storage, and network to cloud consumers on demand. It comes in different flavors that includes cloud deployment models and cloud service models.

Cloud deployment models describe the way cloud resources are deployed, such as behind the firewall and on-premise exclusively for a specific organization, and this is called the private cloud; or cloud resources that are available to all organizations and inpiduals, and this is called the public cloud; or cloud resources that are available to a specific set of organizations that share similar types of interests or similar types of requirements, and this is called the community cloud; or cloud resources that combine two or more deployment models, and this is known as the hybrid cloud.

Cloud service models describe the way cloud resources are made available to cloud consumers. It can be in the form of a pure infrastructure, where virtual machines are accessible and controlled by a cloud consumer or end user, and this is called Infrastructure as a Service (IaaS); or a platform where runtime environments are provided so installation and configuration of all software needed to run application are already available and managed by a cloud service provider, and this is called Platform as a Service (PaaS); or Software as a Service (SaaS), where a whole application is made available by a cloud service provider with the responsibility of infrastructure and platform remaining with the cloud service provider.

Cloud computing has a few characteristics which are significant such as multitenancy, pay-as-you-use (similar to electricity or gas connection), on-demand self-service, resource pooling for better utilization of compute, storage; network resources, rapid elasticity for scaling up and scaling down resources based on needs in an automated fashion, and measured service for billing.

Over the years, usage of different cloud deployment models has varied based on use cases. Initially, the public cloud was used for applications that were considered non-critical while private cloud was used for critical applications where security was a major concern. Hybrid cloud usage evolved over time with experience and confidence in the services provided by cloud service providers.

In a similar way, there was a usage pattern for cloud service models too. As we usually do in a normal traditional environment, it was easier to adopt IaaS as there is complete control. Over time, organizations realized the cost of managing resources in the cloud as the efforts are the same in managing resources, considering security configurations, and other configurations. Hence, IaaS was becoming difficult day by day with the evolution of PaaS. PaaS has evolved over the years and its approach is much wider, and its services include multiple programming languages such as .NET, Java, PHP, Python, and Ruby.

In simple English, PaaS provides infrastructure as well as a runtime environment to deploy an application. The difference is the end user doesn't have control on infrastructure while we can configure a runtime environment and debug an application remotely and troubleshoot issues to some extent. There are PaaS offerings where you can have dedicated infrastructure resources for application deployment, but even in that case, control of infrastructure is in the hands of cloud service providers. In short, we as cloud users need not to worry about downloading different web servers, database servers, and other required software and install them on a machine and maintain them. We don't even need to worry about updating them to newer versions. Cloud service providers are responsible for maintaining availability of the application and its resources. However, as users, we need to follow best practices to configure applications to have a highly available application considering different services provided by the cloud service provider.