Split brain with only two nodes

[balbirthomas]

The current implementation of this Elasticsearch charm protects against "Split Brain" problem but dynamically setting the minimum master nodes parameter. However if the administrator chooses to deploy exactly two nodes then a network partition can still lead to a split brain because each node will find it has quorum (1 minimum master node). How do we protect against this problem ? Shall we explicitly document this in the README ? Is there a better way ?

[jameinel]

The normal rules for this is floor(N/2)+1 guaranteeing a majority. So for 2 nodes they would both have to be together 2/2+1=2. That is why people recommend always going to odd configurations. Because even ones still have the chance to fail but don't have the extra redundancy to keep going. (if either node fails you shouldn't proceed because you don't know if you have split brain)

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On Fri, Oct 23, 2020, 05:50 Balbir Thomas ***@***.***> wrote: The current implementation of this Elasticsearch charm protects against "Split Brain" problem but dynamically setting the minimum master nodes parameter. However if the administrator chooses to deploy exactly two nodes then a network partition can still lead to a split brain because each node will find it has quorum (1 minimum master node). How do we protect against this problem ? Shall we explicitly document this in the README ? Is there a better way ? — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#21>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AABRQ7MZIQUFBTGXTBM4QTDSMFNWLANCNFSM4S4MUKXQ> .

[balbirthomas]

If quorum in a two node cluster is 2, then wouldn't any network partition make the system inoperable, or at least writes would not be possible ?