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Weighted Voting for Replicated Data By David K. Gifford Weighted Voting for Replicated Data by David K. Gifford * CSL-79-14 September, 1979 In a new algorithm for maintaining replicated data, every copy of a replicated file is assigned some number of votes. Every transaction collects a read quorum of r votes to read a file, and a write quorum of w votes to write a file, such that r + w is greater than the total number of votes assigned to the file. This ensures that there is a non-null intersection between every read quorum and every write quorum. Version numbers make it possible to determine which copies are current. The reliability and performance characteristics of a replicated file can be controlled by appropriately choosing r, w, and the file's voting configuration. The algorithm guarantees serial consistency, admits temporary copies in a natural way by the introduction of copies with no votes, and has been implemented in the context of an application system called Violet. CR Categories: 4.3, 4.35, 4.33, 3.81 Key Words and Phrases: weighted voting, replicated data, quorum, file system, file suite, representative, weak representative, transaction, locking, computer network