MongoDB Documentation, Release 3.0.4 Step 2: Add each prospective member to the replica set. When you add a member to the replica set, Initial Sync (page 594) copies the data from the primary to the new member. This document describes the process for creating backups and restoring data using the utilities provided with Mon- goDB. Because all of these tools primarily operate by interacting with a running mongod instance, they can impact the performance of your running database. Not only do they create traffic for a running database instance, they also force the database to read all data through memory. When MongoDB reads infrequently used data, it can supplant more frequently accessed data, causing a deterioration in performance for the database’s regular workload. No matter how you decide to import or export your data, consider the following guidelines: MongoDB Backup Methods (page 184) or MongoDB Cloud Manager Backup documentation 99 for more information on backing up MongoDB instances. Additionally, consider the following references for the MongoDB import/export tools: The mongorestore and mongodump utilities work with BSON (page 178) data dumps, and are useful for creating backups of small deployments. For resilient and non-disruptive backups, use a file system or block-level disk snapshot function, such as the methods described in the MongoDB Backup Methods (page 184) document. Use these tools for backups if other backup methods, such as the MongoDB Cloud Manager 100 or file system snapshots (page 243) are unavailable. Step 1: Ensure that the data directories on the prospective replica set members are empty. Back Up and Restore with MongoDB Tools See also: Binary BSON Dumps $^{99}$https://docs.cloud.mongodb.com/tutorial/nav/backup-use/ $^{100}$https://cloud.mongodb.com/?jmp=docs 249 5.2. Administration Tutorials • mongoimport • mongoexport • mongorestore • mongodump • Test backups and exports by restoring and importing to ensure that the backups are useful. • Make sure that the backups reflect a consistent data state. Export or backup processes can impact data integrity (i.e. type fidelity) and consistency if updates continue during the backup process. • Do not create or apply exports if the backup process itself will have an adverse effect on a production system. • Label files so that you can identify the contents of the export or backup as well as the point in time the ex- port/backup reflect.