2.17.3.1 Quorum Consensus

Consider set of replicas, where replicated objects have version numbers at each replica.

1. Assign a weighting of votes to each replica, indicating importance.
2. For client to perform operation, it must gather votes for all the replicas it can talk to (denote X).
3. X$\ge$ votes set for read quorum R to enable read
4. X$\ge$ votes set for write quorum W to enable write.
5. As long as
   • W > half the total number of votes
   • R + W > total number of votes in group
   Each Read quorum and each write quorum will have at least one member in common.