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MongoDB Backup Methods¶
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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 provides backup methods to support different requirements and configurations:
Backup Methods¶
Backups with MongoDB Cloud Manager¶
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 Backup offers point in time recovery of MongoDB replica sets and a consistent snapshot of sharded clusters.
MongoDB Cloud Manager achieves point in time recovery by storing oplog data so that it can create a restore for any moment in time in the last 24 hours for a particular replica set or sharded cluster. Sharded cluster snapshots are difficult to achieve with other MongoDB backup methods.
To restore a MongoDB deployment from an MongoDB Cloud Manager Backup snapshot, you download
a compressed archive of your MongoDB data files and distribute those
files before restarting the mongod
processes.
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.
Backup by Copying Underlying Data Files¶
You can create a backup by copying MongoDB’s underlying data files.
If the volume where MongoDB stores 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 systems snapshots are an operating system volume manager feature, and are not specific to MongoDB. The mechanics of snapshots depend on the underlying storage system. For example, if you use Amazon’s EBS storage system for EC2 supports snapshots. On Linux the LVM manager can create a snapshot.
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 system, you must disable the balancer and capture a snapshot from every shard and a config server at approximately the same moment in time.
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 create
smaller backups.
For more information, see Backup and Restore with Filesystem Snapshots and Backup a Sharded Cluster with Filesystem Snapshots documents for complete instructions on using LVM to create snapshots. Also see Back up and Restore Processes for MongoDB on Amazon EC2.
Backup with mongodump
¶
The mongodump
tool reads data from a MongoDB database and
creates high fidelity BSON files. The mongorestore
tool can populate a MongoDB database with the data from these BSON
files. These tools are simple and efficient for backing up small
MongoDB deployments, but are not ideal for capturing backups of larger
systems.
mongodump
and mongorestore
can 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.
To mitigate the impact of mongodump
on the performance of
the replica set, use mongodump
to capture backups from a
secondary member of a replica set.
Alternatively, you can shut down a secondary and use
mongodump
with the data files directly. If you shut down a
secondary to capture data with mongodump
ensure that the
operation can complete before its oplog becomes too stale to continue
replicating.
For replica sets, mongodump
also supports a point in time
feature with the --oplog
option. Applications may continue modifying data while
mongodump
captures the output. To restore a point in time
backup created with --oplog
, use
mongorestore
with the --oplogReplay
option.
If applications modify data while mongodump
is creating a
backup, mongodump
will compete for resources with
those applications.
See Back Up and Restore with MongoDB Tools, Backup a Small Sharded Cluster with mongodump, and Backup a Sharded Cluster with Database Dumps for more information.
Further Reading¶
- Backup and Restore with Filesystem Snapshots
- An outline of procedures for creating MongoDB data set backups using system-level file snapshot tool, such as LVM or native storage appliance tools.
- Restore a Replica Set from MongoDB Backups
- Describes procedure for restoring a replica set from an archived
backup such as a
mongodump
or MongoDB Cloud Manager Backup file. - Back Up and Restore with MongoDB Tools
- The procedure for writing the contents of a database to a BSON (i.e. binary) dump file for backing up MongoDB databases.
- Backup and Restore Sharded Clusters
- Detailed procedures and considerations for backing up sharded clusters and single shards.
- Recover Data after an Unexpected Shutdown
- Recover data from MongoDB data files that were not properly closed or have an invalid state.