Hierarchical Modeling of Availability in Distributed Systems

Salim Hariri, Hasan Mutlu

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


Distributed computing systems are attractive due to the potential improvement in availability, fault-tolerance, performance, and resource sharing. Modeling and evaluation of such computing systems is an important step in the design process of distributed systems. In this paper, we present a two-level hierarchical model to analyze the availability of distributed systems. At the higher level (user level), the availability of the tasks (processes) is analyzed using a graph-based approach. At the lower level (component level), detailed Markov models are developed to analyze the component availabilities. These models take into account the hardware/software failures, congestion and collisions in communication links, allocation of resources, and the redundancy level. A systematic approach is developed to apply the two-level hierarchical model to evaluate the availability of the processes and the services provided by a distributed computing environment. This approach is then applied to analyze some of the distributed processes of a real distributed system, Unified Workstation Environment (UWE), that is currently being implemented at AT&T Bell Laboratories.

Original languageEnglish (US)
Pages (from-to)50-56
Number of pages7
JournalIEEE Transactions on Software Engineering
Issue number1
StatePublished - Jan 1995


  • Availability
  • distributed system availability modeling
  • hierarchical availability modeling
  • reliability
  • task availability
  • task availability Optimization

ASJC Scopus subject areas

  • Software


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