Question

1. Characterize the following three cloud computing models:
   1. What is an IaaS cloud? Give one example system.
   2. What is an PaaS cloud? Give one example system.
   3. What is an SaaS cloud? Give one example system.

Answer 1

a)IaaS Cloud

Infrastructure as a service (IaaS) is a type of cloud computing model that allocates virtualized computing resources to the user through the internet.

• IaaS is one of the main components of cloud computing along with software as a service (SaaS) and platform as a service (PaaS). IaaS is completely provisioned and managed over the internet.
• The IaaS technology helps the users to avoid the cost and complexity of purchasing and managing their own physical servers.
• Every resource of IaaS is offered as an individual service component and the users only have to use the particular one they need. The cloud service provider manages the IaaS infrastructure while the users can concentrate on installing, configuring and managing their software.

Example:

Cloud Hosting

Hosting websites on virtual severs that are created on the pooled resources on the basis of the underlying physical servers.

b)PaaS Cloud

PaaS, or Platform-as-a-Service, is a cloud computing model that provides customers a complete platform—hardware, software, and infrastructure—for developing, running, and managing applications without the cost, complexity, and inflexibility of building and maintaining that platform on-premises.

• The PaaS provider hosts everything—servers, networks, storage, operating system software, databases—at their data center; the customer uses it all for a for a monthly fee based on usage and can purchase more resources on-demand as needed.
• PaaS lets your development teams to build, test, deploy, maintain, update, and scale applications (and to innovate in response to market opportunities and threats) much more quickly and less expensively than they could if you had to build out and manage your own on-premises platform

Example:

Web Apps feature in Azure App Service and Azure Cloud Services (web and worker roles) are an example of PaaS

c) SaaS cloud

Software-as-a-Service, or SaaS for short, is a cloud-based method of providing software to users. SaaS users subscribe to an application rather than purchasing it once and installing it.

Users can log into and use a SaaS application from any compatible device over the Internet. The actual application runs in cloud servers that may be far removed from a user's location.

• A SaaS application may be accessed through a browser or through an app. Online email applications that users access through a browser.
• The difference between SaaS and a software installation on a user's computer is somewhat like the difference between streaming a TV show online and buying all the seasons of the TV show on DVD.

Example:

Office 365, Dropbox, Dynamics CRM Online are perfect examples of SaaS software, subscribers pay a monthly or annual subscription fee, and they get Exchange as a Service (online and/or desktop Outlook) or Storage as a Service (OneDrive and Dropbox).