Assignment of availability objectives to components of heterogenous distributed computer systems

This paper provides a scheme to assign availability objectives to various components of a heterogenous distributed computer system using a `minimum cost' criteria. The availability is viewed from a user (client) perspective rather than the traditional system perspective. The user availability objectives are classified in terms of operational and inherent availabilities. Such a classification enables the designers to take into account the user expectations in a more realistic way thus minimizing the high cost of providing fault tolerant systems. The user availability objectives are then translated into the system availability objectives by relating the availability needs of each distinct user group to system components utilized by that group.