Adaptive Checkpointing with Storage Management for Mobile Environments

Conclusions ~~ The limited stable storage available in mobile-computing environments can make traditional checkpointing and message logging umuitable. Since storage on a mobile liost is not considered stable, most protocols designed for these environments save the checkpoints on base stations. Previous approaches have assumed that the base station always has sufficient disk space for storing checkpoints. If there is not enongh storage available, checkpoints might need to be aborted. This paper describes an adaptive protocol that manages storage for base stations. The protocol integrates leasing storage management with a time-based coordinated checkpointing mechanism. The leasing enables storage managers t o control disk-space effectively. Lcasing prevcnts hanged proccsses horn indefinitely retaining storage and, in addition, garbage colleciion is simple. Time-based checkpointing is integrated with leasing to reduce the number of messages for establishing consistent global states. The checkpointing mechanism uses a 3ievel storage hierarchy to improve checkpointing performance. I’eribKmance was evaluated by both implementation experiments and simulations. Thc results show that: . the adaptive protocol reduccs checkpointing ovcrhead, . the leasing mechanism maintains the desired storage assignment for base stations.