Cloud is a new approach of IT infrastructure organization. It implements different models of certain services providing. SaaS (Software-as-a-Service)IaaS (Infrastructure-as-a-Service) and PaaS (Platform-as-a-Service), the most popular of them, are described below.


Computer infrastructure consisting of virtual platforms (computers) connected in the web is presented to the user. He can customize it for his needs. The user gets the possibility to manage the processing means, the storehouse facilities and other fundamental computing facilities (such as virtual servers and web infrastructure). He can set suitable operating systems and applications there. In point of fact, the user rents an abstract computational capability (including server’s time, disk space and network bandwidth) or uses outsourcing services. The consumer doesn’t manage the main infrastructure of the cloud. Instead he manages operating systems, storages and his own deployed applications.
Here are some of the main IaaS advantages: cost savings, scalability and flexibility, faster time of marketing, high availability, focusing on business growth.
Joyent, Microsoft Azure, Amazon Web Services are the most well-known examples of IaaS.


A platform with installed operating system and perhaps a set of applications is provided to the user. He gets an access to this program platform. The platform includes operating systems, DBMS (Database Management System), applied software, development tools and testware. Actually, the consumer rents the platform for development, storage and management of web applications. The user can customize deployed applications and in some cases the configuration settings of the environment. In the same time, the cloud infrastructure remains to be inaccessible for him.
Here are some of the main PaaS advantages: faster innovation, focusing on resources, staying up to date, getting the best technology, uptime maximization, easy scaling, strengthen security, getting the best support.
Google App Engine, platform are the examples of PaaS.


The provider runs his applications inside the cloud infrastructure. After this he makes them available for the consumer via their interface. It can be web/desktop interface or API, for instance. Consumers cannot control the infrastructure of the cloud including the web, servers, operating systems, data storages and so on. Often they cannot even change the settings of the certain application.
Here are some of the main SaaS benefits: lower costs, seamless upgrades, scalability, easy to use, short time to benefit.
Twitter, Skype, Flickr, WebEx and many other services are the examples of SaaS.
Depending on service type cloud systems automatically optimize the use of resources carrying out all necessary measurements.
Along with SaaS, IaaS and PaaS there are a lot of other service models such as Everything as a Service, Hardware as a Service, Workplace as a Service, Data as a Service, Security as a Service. These models will be described in our farther posts.

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