MongoDB Tag-Aware Sharding Workflow

I wonder the work flow of sharding cluster in Tag-Aware Sharding. --- Sharding Status --- sharding version: { "_id" : 1, "version" : 3, "minCompatibleVersion" : 3, "currentVersion" : 4, "clusterId" : ObjectId("546df06d63a15917a8356f4e") } shards: { "_id" : "shard0000", "host" : "hadoop4:27017", "tags" : [ "TR" ] } { "_id" : "shard0001", "host" : "hadoop5:27018", "tags" : [ "US" ] } { "_id" : "shard0002", "host" : "hadoop6:27017", "tags" : [ "OTHER" ] } databases: { "_id" : "admin", "partitioned" : false, "primary" : "config" } { "_id" : "inventory", "partitioned" : true, "primary" : "shard0000" } In tag-aware sharding , with mongorestore command via mongos , first all data writes to PrimaryDatabase and then migrate the appropriate chunks ? Or it can fill the appropriate chunk according to tagRange at the beggining of the insert? For example , when i insert {country:"US",keyword:"abc"} document , at first it goes to shard0001 or goes to the primary database shard0000 and then chunk migration to shard0001?