Orphan-Free Consistent Condition for Log-Based Checkpointing and Rollback Recovery Scheme

The fundamental goal of the log-based fault-tolerant scheme is to bring the system into a consistent global state without any orphan inconsistence. However, the existing Alvisi’s No-Orphans Consistency Condition is only sufficient on condition that the set of local checkpoints of failure processes keep consistent always. Independent of the specific log-based checkpointing and rollback-recovery fault tolerant scheme, an extended orphan-free consistency condition is derived based on PWD assumption in this paper. The definitions of the orphan inconsistence among the process state and the nondeterministic event during a rollback recovery were extended. Finally the essential requirement for message logs was specified to eliminate the possible orphan inconsistence among the process state during a rollback recovery. By contrast, the proposal is a practical and efficient constraint for the orphan-free recovery. Orphan-Free Consistent Condition for Log-Based Checkpointing and Rollback Recovery Scheme