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Fix quorum formula in consensus.mdx (#8166) 

[Add & Remove Servers](https://learn.hashicorp.com/consul/day-2-operations/servers)
guide uses `(N/2)+1` quorum formula.  So does the
[Raft implementation](5927dcda05/raft.go (L909)).

Consensus Protocol document uses `(n+1)/2` formula.
This formula is not only different, it conflicts with the
[Deployment Table](https://www.consul.io/docs/internals/consensus.html#deployment_table)
in the same document; e.g., (6+1)/2 = 3, not 4.

Replace `(n+1)/2` with `(N/2)+1` in Consensus Protocol document.
pull/8182/head
Valery V. Vorotyntsev 2020-06-24 15:23:36 +03:00 committed by GitHub
parent 2a95289f56
commit 3098bc8593
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@ -38,8 +38,8 @@ There are a few key terms to know when discussing Raft:
- Peer set - The peer set is the set of all members participating in log replication. - Peer set - The peer set is the set of all members participating in log replication.
For Consul's purposes, all server nodes are in the peer set of the local datacenter. For Consul's purposes, all server nodes are in the peer set of the local datacenter.
- Quorum - A quorum is a majority of members from a peer set: for a set of size `n`, - Quorum - A quorum is a majority of members from a peer set: for a set of size `N`,
quorum requires at least `(n+1)/2` members. quorum requires at least `(N/2)+1` members.
For example, if there are 5 members in the peer set, we would need 3 nodes For example, if there are 5 members in the peer set, we would need 3 nodes
to form a quorum. If a quorum of nodes is unavailable for any reason, the to form a quorum. If a quorum of nodes is unavailable for any reason, the
cluster becomes _unavailable_ and no new logs can be committed. cluster becomes _unavailable_ and no new logs can be committed.