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Asked: 2026-06-10T06:39:48+00:00

in a 3-node replicaSet why when 2 are down the third become SECONDARY and

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in a 3-node replicaSet why when 2 are down the third become SECONDARY and not PRIMARY?

I want to have 2 mongod inside a DataCenter and one outside, so if the Datacenters fails I wanna the third outside mongod becomes the Primary.

It’s possible without and arbiter?

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1 Answer

  1. Editorial Team

    Ok, found response:

    http://tebros.com/2010/11/mongodb-arbiters-with-only-two-replicas/

    What happend?! It turns out that when a mongod instance is isolated, it cannot vote for itself to be primary. This makes sense when you think about it. If a network link went down and separated your two replicas, you wouldn’t want them both to elect themselves as primary. So in my case, when rep1-1 noticed that it was isolated from the rest of the replica set, it made itself secondary and stopped accepting writes.

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