Should I disable MongoDB balancer to prevent moveChunk to block database due to "W" lock
To see your &quot;real&quot; chunk distribution count between shards, use command sh.status() at mongos.
As you know, result should show that every shard have more or less same amount of chunks.
Yes, you can disable the balancer and if you really use hashed sharding key, end result should be same as if you keep balancer running. Check that sh.status() carefully, I think that you have there something else sharded too, something what don't use hashed sharding key.
On case when movechunks happen even you have hashed shardingkey is of course situtation where you have added new shard to the cluster. That new shard is empty and system starts to fill it.