Convert Sharded Cluster to Replica Set¶
This tutorial describes the process for converting a sharded cluster to a non-sharded replica set. To convert a replica set into a sharded cluster Convert a Replica Set to a Replicated Sharded Cluster. See the Sharding documentation for more information on sharded clusters.
Convert a Cluster with a Single Shard into a Replica Set¶
Reconfigure the application to connect to the primary member of the replica set hosting the single shard that system will be the new replica set.
Optionally remove the --shardsrv option, if your mongod started with this option.
Changing the --shardsrv option will change the port that mongod listens for incoming connections on.
The single-shard cluster is now a non-sharded replica set that will accept read and write operations on the data set.
You may now decommission the remaining sharding infrastructure.
Convert a Sharded Cluster into a Replica Set¶
With the sharded cluster running, deploy a new replica set in addition to your sharded cluster. The replica set must have sufficient capacity to hold all of the data files from all of the current shards combined. Do not configure the application to connect to the new replica set until the data transfer is complete.
Stop all writes to the sharded cluster. You may reconfigure your application or stop all mongos instances. If you stop all mongos instances, the applications will not be able to read from the database. If you stop all mongos instances, start a temporary mongos instance on that applications cannot access for the data migration procedure.
Not all collections on all databases are necessarily sharded. Do not solely migrate the sharded collections. Ensure that all databases and all collections migrate correctly.
The application will now use the un-sharded replica set for reads and writes. You may now decommission the remaining unused sharded cluster infrastructure.