CAAS:Trading Consistency for Availability

As more and more charities and libraries move to cloud services, this technology is no longer novel; it's becoming the dominant paradigm in IT. A cloud storage facility is a need of an hour as it facilitates elasticity–so resource allocation can get bigger or smaller depending on a users’ demand, Elasticity enables scalability–so that the cloud can scale up when demand is high and down for less demand (e.g. allows for scale when an application in the cloud adds users, etc.), Resource Pooling, On Demand, Self-Service Provisioning i.e client can request desire service from cloud vendor and 24*7 service i.e high availability at cheapest price .But the key hindrance come when we need high availability;as it needed to create plenty of copies of single file and at different geography .To attain high consistency more money is needed. In this paper, we have presented unique, innovative, efficient and effective consistency as a service (CaaS) model, which consists of a various large capacity data clouds and small audit clouds .Data clouds are used to store clients actual data offered by Cloud vendors like Google, Amazon, Microsoft, etc .and Audit cloud are used to check consistency of cloud is maintained accurately or not. At the last we have applied traditional approach to audit purpose i.e Heuristic Auditing Strategy which uses 2 algorithm viz Local and Global Auditing Strategy. Loosely synchronized clock is needed to audit purpose. Heuristic Auditing Strategy is used to find violations in consistency terms i.e. document is modified or safe.