In these recent years cloud computing paradigm has achieved widespread adoption. Its success is because of large customers' ability to use services on demand with a pay-as-you-go pricing model. Low costs and high flexibility make migrating to the cloud computing. Though having advantages, however, many companies hesitate to \"Move to the cloud\", mainly because of problems related to service facing at availability, data lock-in, and legal uncertainties. Lock in is made particularly problematic. But, even though public cloud availability is generally high, outages still occur businesses locked into such a cloud are essentially at a standstill until the cloud is back online.