Description: The paper discusses the main problems related to development and research of service availability models of distributed cloud systems. Semi-Markov service availability models of distributed cloud system depending on resource type, principle of creating the model, presence of backup always-on server and other criteria are proposed. Structural and parametric synthesis of the proposed models is performed. The obtained accessibility coefficient value of the composite resource based on the characteristics of Semi-Markov processes is analyzed.
Keywords: distributed cloud architecture, peer-to-peer networks, Semi-Markov processes, cloud services, accessibility, availability, reliability