In our production enviroment, one chunk balance takes almost 300s. If we want to balance 100G data, it will take a very long time.
An available method is: when moveChunk, don't delete data at step6, finally we delete all the data one by one in slave using standonly instance.
But i'm not sure it's right, because data are not delete after balance.By the way, we only query by a given shardkey.

Thanks.