MongoDB Documentation, Release 3.0.4 11.6.12 What information do arbiters exchange with the rest of the replica set? 11.6.13 Which members of a replica set vote in elections? 11.6.14 Do hidden members vote in replica set elections? See also: 11.6.15 Is it normal for replica set members to use different amounts of disk space? See also: See Arbiters never receive the contents of a collection but do exchange the following data with the rest of the replica set: If your MongoDB deployment uses TLS/SSL, then all communications between arbiters and the other members of the replica set are secure. See the documentation for Configure mongod and mongos for TLS/SSL (page 342) for more information. Run all arbiters on secure networks, as with all MongoDB components. The overview of Arbiter Members of Replica Sets (page ?? ). All members of a replica set, unless the value of votes is equal to 0 , vote in elections. This includes all delayed (page 570), hidden (page 569) and secondary-only (page 567) members. Arbiters (page ?? ) always vote in elections and always have 1 vote. Additionally, the state of the voting members also determine whether the member can vote. Only voting members in the following states are eligible to vote: Replica Set Elections (page 580) Hidden members (page 569) of replica sets do vote in elections. To exclude a member from voting in an election , change the value of the member’s votes configuration to 0 . Replica Set Elections (page 580) Yes. Factors including: different oplog sizes, different levels of storage fragmentation, and MongoDB’s data file pre- allocation can lead to some variation in storage utilization between nodes. Storage use disparities will be most pro- nounced when you add members at different times. 771 11.6. FAQ: Replication and Replica Sets • ROLLBACK • ARBITER • RECOVERING • SECONDARY • PRIMARY • Credentials used to authenticate the arbiter with the replica set. All MongoDB processes within a replica set use keyfiles. These exchanges are encrypted. • Replica set configuration data and voting data. This information is not encrypted. Only credential exchanges are encrypted.