Restore a Replica Set from MongoDB Backups¶

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This procedure outlines the process for taking MongoDB data and restoring that data into a new replica set. Use this approach for seeding test deployments from production backups or as part of disaster recovery.

Important

You cannot restore a single data set to three new mongod instances and then create a replica set. If you copy the data set to each mongod instance and then create the replica set, MongoDB will force the secondaries to perform an initial sync. The procedures in this document describe the correct and efficient ways to deploy a restored replica set.

You can also use mongorestore to restore database files using data created with mongodump. See Back Up and Restore with MongoDB Tools for more information.

Restore Database into a Single Node Replica Set¶

1

Obtain backup MongoDB Database files.¶

The backup files may come from a file system snapshot. The MongoDB Cloud Manager produces MongoDB database files for stored snapshots and point in time snapshots. For Ops Manager, an on-premise solution available in MongoDB Enterprise Advanced, see also the Ops Manager Backup overview.

2

Start a `mongod` using data files from the backup as the data path.¶

Start a mongod instance for a new single-node replica set. Specify the path to the backup data files with --dbpath option and the replica set name with the --replSet option. For config server replica set (CSRS), include the --configsvr option.

mongod --dbpath /data/db --replSet <replName>

3

Connect a `mongo` shell to the `mongod` instance.¶

For example, to connect to a mongod running on localhost on the default port of 27017, simply issue:

mongo

4

Initiate the new replica set.¶

Use rs.initiate() on one and only one member of the replica set:

rs.initiate( {
   _id : <replName>,
   members: [ { _id : 0, host : <host:port> } ]
})

MongoDB initiates a set that consists of the current member and that uses the default replica set configuration.

Add Members to the Replica Set¶

MongoDB provides two options for restoring secondary members of a replica set:

Manually copy the database files to each data directory.
Allow initial sync to distribute data automatically.

Note

If your database is large, initial sync can take a long time to complete. For large databases, it might be preferable to copy the database files onto each host.

Copy Database Files and Restart `mongod` Instance¶

Use the following sequence of operations to “seed” additional members of the replica set with the restored data by copying MongoDB data files directly.

1

Shut down the `mongod` instance that you restored.¶

Use --shutdown or db.shutdownServer() to ensure a clean shut down.

2

Copy the primary’s data directory to each secondary.¶

Copy the primary’s data directory into the dbPath of the other members of the replica set. The dbPath is /data/db by default.

3

Start the `mongod` instance that you restored.¶

4

Add the secondaries to the replica set.¶

In a mongo shell connected to the primary, add the secondaries to the replica set using rs.add(). See Deploy a Replica Set for more information about deploying a replica set.

Update Secondaries using Initial Sync¶

Use the following sequence of operations to “seed” additional members of the replica set with the restored data using the default initial sync operation.

1

Ensure that the data directories on the prospective replica set members are empty.¶

2

Add each prospective member to the replica set.¶

When you add a member to the replica set, Initial Sync copies the data from the primary to the new member.

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