Accession Number:

ADA091144

Title:

A Performance-Reliability Model for Computing Systems,

Descriptive Note:

Corporate Author:

CARNEGIE-MELLON UNIV PITTSBURGH PA DEPT OF COMPUTER SCIENCE

Personal Author(s):

Report Date:

1980-01-10

Pagination or Media Count:

26.0

Abstract:

In this paper some measures are presented that characterize both the performance and reliability of digital computing systems in time sharing environments from a user viewpoint. The measures Apparent Capacity and Expected Elapsed Time required to correctly execute a given program are based on a mathematical model built upon traditional assumptions. The model is a hybrid in that is uses statistics gathered from a real system while giving analytical expressions for other statistics such as the Expected Elapsed time. The main parameters of the model are the system workload and the distribution of the time between errors. Although still limited because of the restrictive assumptions used, the model gives quantitative results about how much a user can expect from a time sharing system, as a function of the system workload and reliability. For example, this study measured a four to one range in mean time to system failure as a function of system load. For the maximum load period measured the model predicts a 40 contribution from system unreliability to expected computation time for a program that could require 30 minutes of CPU time in an unloaded situation. Author

Subject Categories:

  • Computer Programming and Software
  • Computer Hardware
  • Computer Systems

Distribution Statement:

APPROVED FOR PUBLIC RELEASE