A Dynamic majority determination algorithm for reconfiguration of network partitions

We present a conservative consistency and recovery conlrol algorilhm for replicated files in the presence of network partitioning due to communication link failures. This algorithm supports partial replication, provides non-blocking operations by allowing update access to a file in that file's majority partition, and brings all copies up-ta-date on all sites whenever the communication links among them are repaired. This algorithm belongs to the class of dynamic voting algorithms proposed in the recent literature. When the communication link among some partitions is reestablished, the algorithms proposed so far do not always allow the merge (reconciliation) of these partitions 10 fonn a single partition. A merge condition has 10 be satisfied to avoid possible inconsistencies. This is undesirable because in a system with more than one replicated file, two or more partitions cannOl be integrated to fonn a single partition if anyone of the replicated files in these partitions does not satisfy the merge condition. This restricl.ion might cause the system to remain partitioned for a long time even if communication links are repaired. (In the previous papers, such a problem is not addressed since a system with only one replicated file is assumed.) The algorithm proposed in this paper releases such merge condi______~"~·o~o~an=d'_"in"'te~tes the partitions whenev(Llh.e_communicaLion link failure.is.repaired, , thus providing a higher degree of availability. This work fonnalizes the presentation of algorithms and data structures for implementation.