Config DB

Generally, never write data to this.
It is maintained by mongo.
It DOES have useful in it.

Check it out

connect to the mongos instance of a sharded cluster && get some shard deets

sh.status()

THAT data is in the config db

use config
show collections

# show each db in the cluster as a document
# partitioned means sharding has been enabled
db.databases.find().pretty()

# return deets on collections that have been sharded
# show what field they have been sharded on
db.collections.find().pretty()

# host name of shards
db.shards.find().pretty()

# each chunk per collection is returned as a doc
# inclusive min
# exclusive max
db.chunks.find().pretty()

# mongos processes on the cluster
# the mongo version is included
db.mongos.find().pretty()

Page Tags:

database

mongodb

replication

sharding

horizontal scaling