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I have a replicaset that's showing multiple system.replset collection in the local db.

replset1:PRIMARY> show collections;

Running db.system.replset.find() returns the documents from both with out error.

They are different versions, one showing the current membership, another an older setup. I haven't seen this before. Is this expected?

I'm not really seeing any problems from the mongo or application side, this just seems strange. The duplicates are present on the primary and secondaries.

Should .remove({"version":}) be safe?

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I've never seen this before (well, I've seen multiple collections with the same name in a couple of Google Group posts, but nothing reproducible). It looks like a bug, assuming that there are no non-printable characters in one of the collection names. What version are you using? Does running .validate(true) (warning: blocking/intensive operation) on the local DB say there are errors? – Adam C Oct 8 '13 at 11:35

I ran into this issue while trying to reconfigure my replicaset. db.system.replset.find().pretty() yielded two replicasets with different versions and different members. Running db.system.replset.remove({"version":199}) ended up removing the bad replicaset configuration. Reconfiguring my replicaset worked after that.

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