Implementing Sharding

• How do you start the config server(s)?

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  • In production have 3 separate config servers
  • Add a DNS or "hosts" file host name for each config server
  • Make a data folder (i.e. /data/configdb)
  • mongod --configsvr --dbpath path-to-data-folder --port 27019

• How do you start the mongos instance(s)?

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  • Assign a DNS or "hosts" file name to the mongos instance
  • mongos --port 27018 --configdb config-server-host-1, config-server-host-2, etc.

• How do you add shards to the cluster?

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  • Connect to the mongos instance:
  • mongo --host mongos-hostname --port 27018
  • Add shard to stand-alone MongoDB instance:
  • sh.addShard("hostname:port")
  • Add shard to a MongoDB replica set:
  • sh.addShard("rs/hostname:port")
  • Where "rs" is the replica set identifier

• How do you enable sharding for a database?

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  • Connect to the mongos instance:
  • mongo --host mongos-hostname --port 27018
  • Enable sharding for database "db-name":
  • sh.enableSharding("db-name")

• How do you enable sharding for a collection

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  • Identify one or more fields to be used as the shard key
  • If the collection contains data:
  • Create an index on the shard key field(s): ensureIndex()
  • Enable sharding for the collection:
  • sh.shardCollection("db-name.collection",{shard_key_field_1: 1 [,shard_key_field_2: 1]})

• How can you confirm sharding is successful?

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  • Connect to the mongos instance:
  • mongo --host mongos-hostname --port 27018
  • sh.status()