A scheme for maintaining consistency and availability of replicated files in a partitioned distributed system

A dynamic voting scheme is presented that enhances the availability of replicated files in a distributed system in the presence of network partitions. In such situations, the proposed scheme maintains consistency of replicated files by imposing the following constraint; a node can commit a file update only if its current enclosing group is a majority of the nodes that participated in the most recent update on the file. Thus, the number of nodes that constitutes a majority is reduced dynamically upon successive partitions. Compared to other dynamic voting schemes, the proposed scheme provides higher availability by taking into account partitions that occur between successive file updates. Towards this end, each node maintains, for each file copy, a view of the network in terms of partition groups. When a file update is attempted, the node updates its view by taking into account partitions occurred since previous update. It refines the view, further using views held by other reachable nodes. Another merit of the proposed scheme is that it does not require failures and repairs of links and nodes to be detected instantaneously by all nodes. Different nodes may have different views of the network at any time