Recoverable Mobile Environments: Design and Trade-oo Analysis

The mobile wireless environment poses challenging fault-tolerant data management problems due to mobility of users, and limited bandwidth on the wireless link. Traditional fault-tolerance schemes, therefore, cannot be directly applied to these systems. Mobile systems are often subject to environmental conditions which can cause loss of communications or data. Because of the consumer orientation of most mobile systems, run-time faults must be corrected with minimal (if any) intervention from the user. The fault-tolerance capability must therefore be self-contained. Schemes for recovery upon a failure of a mobile host are presented here. This report portrays the limitations of the mobile wireless environment, and its impact on recovery protocols. To this eeect, extensions to existing traditional recovery schemes are presented which suit the mobile environment. The performance of these schemes has been analyzed to determine those environments where a particular recovery scheme is best suited. The performance of the recovery schemes mainly depends on (i) the cost of wireless transmission, (ii) the communication-mobility ratio of the user, and (iii) the failure rate of the mobile host.