Updating a mongoCluster

Question

We have Mongodb 3.2.6 as a cluster with 2 arbiter and 2 working data nodes running.

Now we want to update to version 3.4.3.

What is the intended way of doing this?

1. Can I update one by one and will replication with mixed versions be a supported scenario?
2. Do I have to remove individual node from cluster and update them then add back to cluster?

I am open to any suggestion with best practices.

Answer 1

OK, First thing first... Two arbiters and two data nodes is not a good configuration.

Vote count should be odd, not even. So two data nodes and one arbiter.

But what comes to update, answer is with "rolling manner"..

1. Upgrade arbiter(s)
2. Upgrade secondary
3. Step down primary and when it's secondary/stopped, upgrade it.

That's it!