An algorithm for dynamic data distribution

The replication scheme of a distributed database determines how many replicas of each object are created, and to which processors these replicas are allocated. This scheme critically affects the performance of a distributed system, since reading an object locally is less costly than reading it from a remote processor. Therefore in a read-intensive network a widely distributed replication is mandated. On the other hand, an update of an object is usually written to all, or a majority of the replicas, and therefore in a write-intensive network a narrowly distributed replication is mandated. In other words, the optimal replication scheme depends on the read-write pattern for each object. The authors propose a practical algorithm, called dynamic-data-allocation (DDA), that changes the replication scheme of an object (i.e. the processors which store a replica of the object) dynamically as the read-write pattern of the object changes in the network. They assume that the changes in the read-write pattern are not known a priori.<>