Improved area-difference-based recovery information placement

In mobile computing systems, message logging can be used to provide fault tolerance for mobile hosts. Due to the mobility of mobile hosts, their recovery information, including logged messages and checkpoints, may spread throughout mobile support stations. During recovery, there will be a considerable cost for the collection of recovery information. To speed up recovery and to reduce the failure-free overhead, an improved area-difference-based scheme is proposed. It tries to keep recovery information evenly spreading over an area. Only part of recovery information needs to be migrated for controlling the distribution of recovery information. To reduce the migration cost, a light-weight migration is also proposed. In the performance study, we give an analysis of the probability that the light-weight migration takes place.