
Cloud computing is the development of distributed computing, parallel computing, grid computing and virtualization technologies which define the shape of a new era. In this paper, we explore the concept of cloud architecture and compares cloud computing with grid computing. We identified several challenges from the cloud computing adoption perspective and we also highlighted the interoperability issue that deserves substantial further research and development. Cloud computing is a completely internet dependent technology where client data is stored and maintain in the data center of a cloud provider. Limited control over the data may incur various security issues and threats. The challenges for adopting cloud computing such as well managed service level agreement, interoperability, privacy and reliability. This research paper outlines what cloud computing is, the various cloud models and the main security risks and issues that are currently present within the cloud computing industry.