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3 major cloud service modes: “IAAS, PAAS and SAAS”

When moving to Cloud Computing, it helps to distinguish between different aspects of Cloud Computing, assess their own situation in order to decide what types of solutions are appropriate for your unique needs.

Indeed, 3 main models of Cloud use are currently emerging: the infrastructure Cloud (IAAS or Infrastructure as a Service), the application Cloud (PAAS or Platform as a Service) and software on demand (SAAS or Software as a Service). All have different characteristics:

IAAS “Infrastructure As A Service”

An IAAS-type cloud provides a virtualized, distributed and highly automated IT infrastructure foundation to meet the requirements of putting an enterprise’s applications into production. This infrastructure foundation is made up of a group of resources (servers, networks, storage) accessible in a granular fashion and with multiple predetermined service levels. The basic unit of consumption in an infrastructure cloud is the virtual machine. The infrastructure cloud is also generally billed according to the time of use of this VM, its consumption in number of storage and network inputs, outputs.

PAAS “Platform As A Service”

This type of service is located just above the previous one, so the operating system and infrastructure tools are the responsibility of the supplier. The consumer has control of the applications and can add their own tools. The situation is therefore analogous to that of web hosting where the consumer rents the operation of servers on which the necessary tools are previously placed and controlled by the provider. The difference being that the systems are shared and offer great elasticity – the ability to adapt automatically to demand, whereas in a traditional web hosting offer the adaptation follows a formal consumer demand.

SAAS “Software As A Service”

Currently, the SAAS model generates the most revenue. In this model, a business accesses an application in hosted mode without having to worry about the infrastructure platform or the software platform. The user buys a feature and consumes it on demand. Microsoft thus offers several of its flagship applications in SAAS mode with Exchange Online, SharePoint Online, Linc Online or Dynamics CRM Online. The SAAS model is often seen as an alternative to the traditional software deployment mode. It offers companies real benefits such as eliminating the need to build and operate the IT infrastructure behind the software in-house. Likewise, it is no longer necessary to manage the processes of updating applications or installing patches, these being the responsibility of the SAAS provider. Finally, the mode of invoicing to the user is often cited as an advantage, especially since most SAAS contracts provide for adjusting the number of licenses upwards or downwards, whereas in the traditional mode, a license purchased is definitively.


“In short, in SAAS we consume, in PAAS we develop and in IAAS we host! ”

In a few words, we can summarize these 3 Cloud service modes in the following table:





-Acronym: Software as a Service-The customer is a user / a company

-The customer pays for a service, only the skills to use this service (administration) are required

-No need for development / infrastructure skills, the supplier is responsible for the infrastructure and the platform

-Billing: Here, the user rents turnkey software. The payment method is often “per user / month”.

-Ex: Office 365 (Exchange, SharePoint, Lync online), CRM Online

-Acronym: Platform as a Service-The client is a developer / a company

-The customer pays to have space to run his code, without worrying about managing / updating the operating system

-No need for infrastructure skills

-Billing: Here, the developer rents a turnkey code execution platform. The billing method can be variable, but often revolves around the factors of CPU usage time, storage space and consumed bandwidth

-Ex: Windows Azure (Compute, Storage, SQL Azure, Service Bus …)

-Acronym: Infrastructure as a Service-The client is an IT Pro / a company

-The customer pays to have a place to run his virtual machine, without worrying about the network or potential hardware incidents.

-No need for network skills (or other load balancing)

-Billing: Here, IT Pro rents a turnkey VM hosting service. The billing mode is similar to PAAS but can also increase to take into account the rental of products installed on the VM (ex: SQL Server, Biztalk, etc.)

-Ex: Windows Azure Virtual Machines


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