Cloud SLA relationships in multi-cloud environment: models and practices

In the past few years, cloud computing has been realized and has achieved advancement. Sincemany cloud systems and providers have been deployed in this world, various models and platforms have been developed to support multiple cloud (i.e., multi-cloud) environments (e.g., inter-cloud, federated cloud, distributed cloud, hybrid cloud, multi-cloud management platform, and cloud service brokerageplatform). Whereas those models provide a multi-cloud environment, they are different according to their objectives, service models, SLA (service level agreement) models, and so on. Even though SLA is considered as a very important issue in cloud computing, SLA relationships in multi-cloud models are not formally described yet. Therefore, in this paper, we introduce various multi-cloud models and analyze the multi-cloud models in term of SLA relationship based on the proposed SLA relationship description model. In addition, this paper introduces open source multi-cloud projects to understand practices in cloud SLA relationships.