Replication nodes obtain data directly from or write data directly to the log-structured storage system, which provides outstanding write performance, while maintaining index structures that provide low-latency read performance as well. The Oracle Berkeley DB Java Edition storage engine pioneered the use of logstructured storage in key/value databases since its initial deployment and has been proven in several open-source NoSQL solutions, such as Dynamo, Voldemort, and GenieDB, as well as in Enterprise deployments. Oracle NoSQL Database uses replication to ensure data availability in the case of failure. Its singlemaster architecture requires that writes are applied at the master node and then propagated to the replicas. In the case of failure of the master node, the nodes in a shard automatically hold a reliable election (using the Paxos protocol), electing one of the remaining nodes to be the master. The new master then assumes write responsibility. When multiple replication nodes reside on a storage node, the system will attempt to insure that no shard has more than one of its replication nodes on a single storage node.