Abstract: Cloud computing is subject to failures which emphasize the need to address user's availability. Availability refers to the system uptime and the system capability to operate continuously. Different techniques can be implemented to increase the system availability. Indeed, cloud service provider is taking the lead in providing highly available and cost effective services. However, these solutions are not always working as it claims. This paper conducts a literature review to investigate different techniques used to ensure the system availability. An analysis of high profile cloud service company is presented to evaluate the availability level of their services and to find out if high availability can be ensured or not.

Keywords: Cloud Computing, High Availability, Cloud service provider, Scalability.