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When deploying MongoDB in production, you should have a strategy for capturing and restoring backups in the case of data loss events.
MongoDB Atlas, the hosted MongoDB service option in the cloud, offers two fully-managed methods for backups:
MongoDB Cloud Manager is a hosted back up, monitoring, and automation service for MongoDB. MongoDB Cloud Manager supports backing up and restoring MongoDB replica sets and sharded clusters from a graphical user interface.
The MongoDB Cloud Manager supports the backing up and restoring of MongoDB deployments.
MongoDB Cloud Manager continually backs up MongoDB replica sets and sharded clusters by reading the oplog data from your MongoDB deployment. MongoDB Cloud Manager creates snapshots of your data at set intervals, and can also offer point-in-time recovery of MongoDB replica sets and sharded clusters.
Tip
Sharded cluster snapshots are difficult to achieve with other MongoDB backup methods.
To get started with MongoDB Cloud Manager Backup, sign up for MongoDB Cloud Manager. For documentation on MongoDB Cloud Manager, see the MongoDB Cloud Manager documentation.
With Ops Manager, MongoDB subscribers can install and run the same core software that powers MongoDB Cloud Manager on their own infrastructure. Ops Manager is an on-premise solution that has similar functionality to MongoDB Cloud Manager and is available with Enterprise Advanced subscriptions.
For more information about Ops Manager, see the MongoDB Enterprise Advanced page and the Ops Manager Manual.
Considerations for Encrypted Storage Engines using AES256-GCM
For encrypted storage engines that use AES256-GCM encryption mode, AES256-GCM requires that every process use a unique counter block value with the key.
For encrypted storage engine configured with AES256-GCM cipher:
Starting in 4.2, if you restore from files taken via “hot”
backup (i.e. the mongod is running), MongoDB can detect “dirty” keys on startup and automatically rollover the database key to avoid IV (Initialization Vector) reuse.
However, if you restore from files taken via “cold” backup (i.e. the mongod is not running), MongoDB cannot detect “dirty” keys on startup, and reuse of IV voids confidentiality and integrity guarantees.
Starting in 4.2, to avoid the reuse of the keys after restoring from a cold filesystem snapshot, MongoDB adds a new command-line option --eseDatabaseKeyRollover. When started with the --eseDatabaseKeyRollover option, the mongod instance rolls over the database keys configured with AES256-GCM cipher and exits.
Tip
AES256-GCM encryption mode, do not make copies of your data files or restore from filesystem snapshots (“hot” or “cold”).You can create a backup of a MongoDB deployment by making a copy of MongoDB’s underlying data files.
If the volume where MongoDB stores its data files supports point-in-time snapshots, you can use these snapshots to create backups of a MongoDB system at an exact moment in time. File system snapshots are an operating system volume manager feature, and are not specific to MongoDB. With file system snapshots, the operating system takes a snapshot of the volume to use as a baseline for data backup. The mechanics of snapshots depend on the underlying storage system. For example, on Linux, the Logical Volume Manager (LVM) can create snapshots. Similarly, Amazon’s EBS storage system for EC2 supports snapshots.
To get a correct snapshot of a running mongod process, you must have journaling enabled and the journal must reside on the same logical volume as the other MongoDB data files. Without journaling enabled, there is no guarantee that the snapshot will be consistent or valid.
To get a consistent snapshot of a sharded cluster, you must disable the balancer and capture a snapshot from every shard as well as a config server at approximately the same moment in time.
For more information, see the Back Up and Restore with Filesystem Snapshots and Back Up a Sharded Cluster with File System Snapshots for complete instructions on using LVM to create snapshots.
cp or rsync¶If your storage system does not support snapshots, you can copy the files directly using cp, rsync, or a similar tool. Since copying multiple files is not an atomic operation, you must stop all writes to the mongod before copying the files. Otherwise, you will copy the files in an invalid state.
Backups produced by copying the underlying data do not support point in time recovery for replica sets and are difficult to manage for larger sharded clusters. Additionally, these backups are larger because they include the indexes and duplicate underlying storage padding and fragmentation. mongodump, by contrast, creates smaller backups.
mongodump¶mongodump reads data from a MongoDB database and creates high fidelity BSON files which the mongorestore tool can use to populate a MongoDB database. mongodump and mongorestore are simple and efficient tools for backing up and restoring small MongoDB deployments, but are not ideal for capturing backups of larger systems.
mongodump and mongorestore operate against a running mongod process, and can manipulate the underlying data files directly. By default, mongodump does not capture the contents of the local database.
mongodump only captures the documents in the database. The resulting backup is space efficient, but mongorestore or mongod must rebuild the indexes after restoring data.
When connected to a MongoDB instance, mongodump can adversely affect mongod performance. If your data is larger than system memory, the queries will push the working set out of memory, causing page faults.
Applications can continue to modify data while mongodump captures the output. For replica sets, mongodump provides the --oplog option to include in its output oplog entries that occur during the mongodump operation. This allows the corresponding mongorestore operation to replay the captured oplog. To restore a backup created with --oplog, use mongorestore with the --oplogReplay option.
However, for replica sets, consider MongoDB Cloud Manager or Ops Manager.
Note
mongodump and mongorestore cannot be part of a backup strategy for 4.2+ sharded clusters that have sharded transactions in progress, as backups created with mongodump do not maintain the atomicity guarantees of transactions across shards.
For 4.2+ sharded clusters with in-progress sharded transactions, use one of the following coordinated backup and restore processes which do maintain the atomicity guarantees of transactions across shards:
See Back Up and Restore with MongoDB Tools and Back Up a Sharded Cluster with Database Dumps for more information.