3-MODE FAILURE MODEL FOR RELIABILITY-ANALYSIS OF DISTRIBUTED PROGRAMS

The distributed program reliability (DPR) is a useful measure for reli ability evaluation of distributed systems. In previous methods, a two- mode failure model (working or failed) is assumed for each computing n ode. However, this assumption is not realistic because data transfer m ay be possible by way of a computing node even when this node can neit her execute programs nor handle its data files. In this paper, we defi ne a new three-mode failure model for representing such a degraded ope rational state of computing nodes, and present a simple and efficient analysis method based on graph theory. In order to represent the degra ded operational state, a given graph expressing a distributed system i s augmented by adding new edges and vertices. By traversing this augme nted graph, the reliability measure can be computed. Examples show the clear difference between the results of our proposed method and those of the previous ones.