561 Copyright © 2016, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. Chapter 24 DOI: 10.4018/978-1-4666-9466-8.ch024 Design Challenges of Cloud Computing ABSTRACT Cloud computing has recently emerged as a new paradigm of computing for hosting and delivering services over the Internet. It replaces computing as a personal commodity by computing as a public utility. It is attractive solution to business owners as it eliminates the requirement for users to plan ahead for provisioning, and allows enterprises to start from the small and increase resources only when there is a rise in service demand. However, despite the signifcant benefts, these technologies present many challenges including lack of security. The chapter presents an advanced survey focusing on cloud com- puting concept. It highlights its key concepts and presents a physical architecture of this environment. Finally, the chapter defnes virtualization technology as a factor for cloud computing surge and discusses security issues that damage these systems. The aim of this chapter is to provide a better understanding of the design challenges of cloud computing. INTRODUCTION With the advent of information technologies, society relies heavily upon software. In fact, software is found in automobiles, airplanes, chemical factories, power stations and numerous other systems in which it plays a critical role. Software or business applications need comput- ing resources and hence important investment in IT infrastructure. The infrastructure is often very costly ranging from a small number of servers to an entire data center. However, provisioning and managing computing resources is so costly. There are three major costs: (1) capital costs, i.e., the cost of buying the hardware, software, and installation costs, (2) maintenance and operation costs, i.e., the cost of personnel to maintain the infrastructure as well as cost of power, cooling, and sever storage, and (3) additional costs, for example, to buy extra hardware and software to Mouna Jouini Institut Supérieur de Gestion, Tunisia Latifa Ben Arfa Rabai Institut Supérieur de Gestion, Tunisia