A stochastic breakdown model for an unreliable web server system and an optimal admission control policy

Ji Hwan Cha, Euiyong Lee

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Web servers have to be protected against overload since overload can lead to a server breakdown, which in turn causes high response times and low throughput. In this paper, a stochastic model for breakdowns of server systems due to overload is proposed and an admission control policy which protects Web servers by controlling the amount and rate of work entering the system is studied. Requests from the clients arrive at the server following a nonhomogeneous Poisson process and each requested job takes a random time to be completed. It is assumed that the breakdown rate of the server depends on the number of jobs which are currently being performed by the server. Based on the proposed model, the reliability function and the breakdown rate function of the server system are derived. Furthermore, the long-run expected number of jobs completed per unit time is derived as the efficiency measure, and the optimal admission control policy which maximizes the efficiency will be discussed.

Original languageEnglish
Pages (from-to)453-466
Number of pages14
JournalJournal of Applied Probability
Volume48
Issue number2
DOIs
StatePublished - Jun 2011

Keywords

  • Breakdown rate
  • Efficiency
  • Optimal admission control policy
  • Reliability function
  • Unreliable server

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