Question

Point out the correct statement.

(a) Splitting is the process MongoDB uses to distribute data of a sharded collection evenly across a sharded cluster

(b) Any mongos instance in the cluster can start a balancing round

(c) When a shard has too many of a sharded collection’s chunks compared to other shards, MongoDB splits balances the chunks across the shards

(d) All of the mentioned

This question was posed to me in an international level competition.

I need to ask this question from Sharding Mechanics topic in division Sharding Concepts, Mechanics and Sharded Cluster of MongoDB

Answer 1

Correct answer is (b) Any mongos instance in the cluster can start a balancing round

For explanation I would say: When a balancer process is active, the responsible mongos acquires a “lock” by modifying a document in the lock collection in the Config Database.