Abstract: Today, cloud computing is a technology in itself is gigantic surpassing all previous information technology (such as cluster, grid, distributed, etc.) of this competitive and challenging world of IT  .In cloud computing the information generated in electronic format are large in quantity . Cloud computing is one of today most existing technologies because of its ability to reduce the cost associated with computing and the flexibility and scalability day  .The need for cloud computing is increasing day and advantages overcome the disadvantage of different first computing techniques . Cloud storage offers online storage, which store data in the form of virtualized pool that is usually hosted by a third party  .The hosting company operates large data in large data centers and in accordance with customer requirements these virtualized data center resources and expose as storage pools that help users to store files or data objects . As the number of users sharing the storage and other resources, it is possible that other customers can access their data. Or human error network connectivity faulty equipment, an insect or any criminal intent can put our cloud storage on the risk and danger . And changes in the cloud also made very frequently; we can call dynamic data.
Keywords: Backup Procedures, Fault tolerance, Authentication, Error Handling, Retrieval models.