How to setup Mongodb operator to deploy a Replicaset with 2 replicas and 1 arbiter

From documentation, it seems that the minimum replicaset replicas number is 3. Why 2 replicas and 1 arbiter is not considered a valid and safe option? I’d would like to understand if this topology has some drawbacks and in case how to achieve it without changing the “allowUnsafeConfigurations” flag.


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Hello, 2 replicas and 1 arbiter is not a configuration we recommend for production use. Think about the case you lose one of the replicas, then you’d only have 1 server left with the data. This is very risky, and also means adding a replacement host will likely impact your primary’s performance due to the initial sync process.

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Hello @Alessandro_Rovetto ,

since MongoDB 4.0 2 nodes + 1 arbiter cannot provide write guarantee. That is why we consider that only 4 nodes + 1 arbiter are safe. Or probable 3 nodes + 2 arbiters.

Please me know if you have any concerns about this decision and if we can support you.

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