Database Reference
In-Depth Information
Preparing the environment
Before jumping into configuring and setting up the cluster network, we have to check some
parameters and prepare the environment.
To enable sharding for a database or collection, we have to configure some configuration
servers that hold the cluster network metadata and shards information. Other parts of the
cluster network use these configuration servers to get information about other shards.
In production, it's recommended to have exactly three configuration servers on different
machines. The reason for establishing each shard on a different server is to improve the
safety of data and nodes. If one of the machines crashes, the whole cluster won't be un-
available.
For the testing and developing environment, you can host all the configuration servers on a
single server. Besides, we have two more parts for our cluster network, shards and
mon-
gos
, or query routers. Query routers are the interface for all clients. All read/write requests
are routed to this module. The query router or
mongos
instance, using configuration serv-
ers, route the request to the corresponding shard.
The following diagram shows the cluster network, modules, and the relationship between
them:
