Cloud computing is a vastly growing information technology and its space continues to evolve at an astounding pace. It provides efficient model for organizations to take services over internet. Its professional services such as computing, software, data storage, hardware and network are growing like no other. Data storage service has been used in engineering, medical, private sectors. Now in many countries government also looks towards cloud to store their data known as g-cloud. In current time if any industry is evaluating technology replacements, upgrades or acquisitions, cloud has to be on their list of considerations. Apart from these cloud services have limitations because of lack in data security due to which in past many time cloud services have been interrupted. Data must be secured in cloud by use of effective encryption algorithms in proper way with the help of data security models. This paper covers data security issues in cloud, data security models and their comparisons.