Change Standalone to WiredTiger
Note
Starting in version 4.2, MongoDB removes the deprecated MMAPv1 storage engine. If upgrading to MongoDB 4.2 from a MongoDB 4.0 deployment that uses MMAPv1, you must upgrade to WiredTiger.
Use this tutorial to change the storage engine of a standalone MongoDB instance to WiredTiger.
Considerations
mongodump and mongorestore
This tutorial uses the mongodump and
mongorestore utilities to export and import data.
Default Bind to Localhost
MongoDB binaries, mongod and
mongos, bind to localhost by default.
The tutorial runs mongodump and
mongorestore from the same host as the
mongod they are connecting to. If run remotely,
mongodump and mongorestore must specify
the ip address or the associated hostname in order to connect to the
mongod.
MongoDB 3.0 or Greater
You must be using MongoDB version 3.0 or greater in order to use the WiredTiger storage engine. If using an earlier MongoDB version, you must upgrade your MongoDB version before proceeding to change your storage engine. To upgrade your MongoDB version, refer to the appropriate version of the manual.
XFS and WiredTiger
With the WiredTiger storage engine, using XFS for data bearing nodes is recommended on Linux. For more information, see Kernel and File Systems.
MMAPv1 Only Restrictions
Once upgraded to WiredTiger, your WiredTiger deployment is not subject to the following MMAPv1-only restrictions:
MMAPv1 Restrictions | Short Description |
|---|---|
Number of Namespaces | For MMAPv1, the number of namespaces is limited to the size of
the namespace file divided by 628. |
Size of Namespace File | For MMAPv1, namespace files can be no larger than 2047 megabytes. |
Database Size | The MMAPv1 storage engine limits each database to no more than
16000 data files. |
Data Size | For MMAPv1, a single mongod instance cannot
manage a data set that exceeds maximum virtual memory address
space provided by the underlying operating system. |
Number of Collections in a Database | For the MMAPv1 storage engine, the maximum number of collections
in a database is a function of the size of the namespace file
and the number of indexes of collections in the database. |
Procedure
Start the mongod you wish to change to WiredTiger.
If mongod is already running, you can skip this step.
Export data using mongodump.
mongodump --out=<exportDataDestination>
Specify additional options as appropriate, such as username and
password if running with authorization enabled. See
mongodump for available options.
Create a data directory for the new mongod running with WiredTiger.
Create a data directory for the new mongod instance that
will run with the WiredTiger storage engine. mongod must have read
and write permissions for this directory.
mongod with WiredTiger will not start with data files created with
a different storage engine.
Update configuration for WiredTiger.
Remove any MMAPv1 Specific Configuration Options from the mongod
instance configuration.
Start mongod with WiredTiger.
Start mongod, specifying wiredTiger as the
--storageEngine and the newly
created data directory for WiredTiger as the --dbpath.
Specify additional options as appropriate, such as
--bind_ip.
Warning
Before you bind your instance to a publicly-accessible IP address, you must secure your cluster from unauthorized access. For a complete list of security recommendations, see Security Checklist. At minimum, consider enabling authentication and hardening network infrastructure.
mongod --storageEngine wiredTiger --dbpath <newWiredTigerDBPath> --bind_ip localhost,<hostname(s)|ip address(es)>
You can also specify the options in a configuration file. To specify the storage engine, use
the storage.engine setting.
Upload the exported data using mongorestore.
mongorestore <exportDataDestination>
Specify additional options as appropriate. See
mongorestore for available options.