2.1. Cloud Service Models In recent years, virtual machines have become a standard developmental object, as well as the prevailing abstraction and the developmental unit in many industries. They represent the smallest common interface which divides the service providers from the developmental organizations. Virtualization enables the existence of dynamic databases in which physical servers provide a large amount of resources that are retrieved as needed. Virtual machines and applications greatly enhance the ability of rapid development and the creation of applications, that is why the key to the future development of cloud computing lies precisely in the combined use of virtual machines and applications [2]. There are three basic classifications …show more content…
Applications are delivered to the user via server interface which can be obtained via the Internet [2]. PaaS model offers quick developmental process, the ease of use and maintenance and the work of different teams, since development teams are connected through PaaS platforms. As in the previous model, the problem of security questions and data compromise emerges, primarily because the data are stored on third-party servers. In addition, PaaS offers less flexibility to developers in creating applications and greatly depends on the Internet connection …show more content…
The same servers contain different users' applications, networks, and storage systems, what, therefore, raises the question of the data security. It offers the ability of increase or decrease of the reserved instances of the cloud according to the principle of "pay as you use" [2]. Its creation does not require the developing infrastructure, there are no maintenance costs, it is significantly cheaper than other cloud models, it is very customizable and has no restrictions on the number of users. Such a large number of users raises a question of security and privacy, whose autonomy is not possible [3]. Community cloud: by using this model, several organizations with common needs, missions and security requirements, share the structure of one cloud. It somewhat resembles the private cloud; it allows the teamwork on the cloud, the division of responsibilities in an organization and it is yet more secure than public cloud. However, safety features do not have the same level of quality as in the private cloud, so it is unsuitable for the use unless there is a need for teamwork on it