Let's look at what components include cluster fragmentation. A slice MongoDB cluster (refer to the official document sharded the Cluster ) is composed of three components, are indispensable:
1.shard: Each slice is a subset of the overall data. Each slice can be deployed as a replica set. It is strongly recommended in a production environment will deploy the patch for the replica set and deploy a minimum of two slices.
2.mongos: act as a query router, provides an interface between client applications and cluster fragmentation. Mongos application directly connected to, one or more may be deployed.
3.config servers: server storage cluster configuration metadata and configuration (including rights related to certification). Starting MongoDB 3.4, you must configure the server to deploy replica set (CSRS, stands for Config Servers Replica Set).
FIG MongoDB slice cluster architecture shown below, from the reference picture.
