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- Replica Set Arbiter
Replica Set Arbiter¶
An arbiter does not have a copy of data set and cannot become a primary. Replica sets may have arbiters to add a vote in elections of for primary. Arbiters allow replica sets to have an uneven number of members, without the overhead of a member that replicates data.
Important
Do not run an arbiter on systems that also host the primary or the secondary members of the replica set.
Only add an arbiter to sets with even numbers of members. If you add an arbiter to a set with an odd number of members, the set may suffer from tied elections. To add an arbiter, see Add an Arbiter to Replica Set.
Example¶
For example, in the following replica set, an arbiter allows the set to have an odd number of votes for elections:
Security¶
Authentication¶
When running with auth
, arbiters exchange credentials with
other members of the set to authenticate. MongoDB encrypts the
authentication process. The MongoDB authentication exchange is
cryptographically secure.
Arbiters use keyfiles
to authenticate to the
replica set.
Communication¶
The only communication between arbiters and other set members are: votes during elections, heartbeats, and configuration data. These exchanges are not encrypted.
However, if your MongoDB deployment uses SSL, MongoDB will encrypt all communication between replica set members. See Connect to MongoDB with SSL for more information.
As with all MongoDB components, run arbiters in trusted network environments.