Security is one of the main issues in the cloud computing business model, followed by privacy, availability and compliance. Data security is the top concern for organizations, especially in shared and multi-tenant environments. In a shared environment, technologies are needed to effectively isolate data and workload. We present different security issues in table #1.Description Issues NoUsing rubber band to prevent DDos attacks Service availability 1Protect data by encryption Data privacy 2Improve virtual machine support, scheduling support flash disks and virtual drives HPC Application Performance 3Data backup/realization, fast hard disk, higher bandwidth LAN switch, bottlenecks in data transfer 4Research and develop scalable storage system Scalable storage 5Provide service protected by reputation like sharing the fate of email reputation 6Use paid models license Software licenses 7Table 1. Issues in cloud computing2.1 Data security: The top The biggest security concern in the cloud is data security. The customer has no idea how the service provider processes and stores customer data. In a public cloud environment, responsibility of the service provider for how it implements effective security controls and protects critical assets. Cloud computing has three different definitions: infrastructure as a service (IaaS), platform as a service (PaaS), and software as a service (SaaS). The three definitions have different security concerns. Network storage, virtualization, and core processing resources are provided by the service provider to customers in the IaaS model in which the customer deploys and runs the software. With IaaS, cloud users have better control over security compared to other models as long as there is no security breach in the virtual machine monitor [4]. With PaaS, customers can deploy their application on cloud infrastructure without installing any tools. . The PaaS service provider must secure the software platform stack. With SaaS, the customer can use the service provider's software through a web browser. In the SaaS model, the overall burden of security falls on the cloud provider and data security is a major challenge when a customer uses the SaaS model. Cloud computing is a distributed system comprising several computers interconnected in virtualized form. Data centers provide the computing power of cloud computing, made up of thousands of servers. Customer data is stored on these servers and the security of this data is a serious issue. Figure 1 shows the layered architecture of data centers. Cloud applications Virtual machines Application server Storage server Table 2. Layered architecture of data centers In the layered architecture of data centers, the lowest layer represents a resource massive physical, for example servers and application servers and these servers are maintained virtualization layer. Cloud applications, for example, business applications, games, social networks and scientific works, run on a higher layer architecture. In a cloud environment, customer data is processed and stored in plain text form and data backup is also a concern..