Interoperability and Portability Approaches in Inter-Connected Clouds: A Review

Inter-connected cloud computing is an inherent evolution of Cloud Computing. Numerous benefits provided by connecting clouds have garnered attraction from the academic as well as the industry sector. Just as every new evolution faces challenges, inter-connected clouds have their own set of challenges such as security, monitoring, authorization and identity management, vendor lock-in, and so forth. This article considers the vendor lock-in problem, which is a direct consequence of the lack of interoperability and portability. An extensive literature review by surveying more than 120 papers has been done to analyze and categorize various solutions suggested in literature for solving the interoperability and portability issues of inter-connected clouds. After categorizing the solutions, the literature has been mapped to a specific solution and a comparative analysis of the papers under the same solution has been done. The term "inter-connected clouds" has been used generically in this article to refer to any collaboration of clouds which may be from the user side (Multi-clouds or Aggregated service by Broker) or the provider side (Federated clouds or Hybrid clouds). Lastly, two closely related issues (Brokers and Meta-scheduling) and the remaining challenges of inter-connected clouds are discussed.