Cloud Computing: Service models, Types, Database and ssues

The evolution of cloud computing over the past few years is potentially one of the major advances in the history of computing. From a user‘s perspective, cloud computing involves performing a task using someone else‘s computers and possibly software. Cloud has given a new meaning to distributed, and off-premises computing. Cloud computing is an architectural model that leverages standardization and consolidation to allow effective and safe sharing of pooled resources. cloud computing refers to the use of scalable, real-time,Internet-based IT services and resources, incorporating beyond SaaS many key technology trends of the 2000s. Although, Cloud offers great benefits, it also introduces a myriad of security threats to the information and data which is now being ported from on-premises to off-premises. This paper discusses the various service models such as IaaS, PaaS, SaaS. Some products offer Internet-based services—such as storage, middleware, collaboration, and database capabilities—directly to users such as Iaas,Paas,Saas.Most cloud computing systems in operation today are proprietary, rely upon infrastructure that is invisible to the research community, or are not explicitly designed to be instrumented and modified by system