For the WiredTiger storage engine, you can specify the maximum size of the cache that WiredTiger will use for all data. This can be done using storage.wiredTiger.engineConfig.cacheSizeGB option.

In MongoDB, WiredTiger is the default storage engine starting from version 3.2. To configure the cache size for WiredTiger, you can use the wiredTiger.cacheSizeGB parameter in the MongoDB configuration file or as a command-line option.

Here’s an example of how you can set the cache size for WiredTiger:

Configuration File (mongod.conf)

Open your MongoDB configuration file (usually named mongod.conf) and add or modify the following line:

storage:

wiredTiger:

engineConfig:

cacheSizeGB: 2

Replace 2 with the desired cache size in gigabytes.

Command-Line Option

You can also specify the cache size directly when starting MongoDB using the --wiredTigerCacheSizeGB option:

mongod --wiredTigerCacheSizeGB 2

Again, replace 2 with the desired cache size in gigabytes.

Keep in mind that the cache size should not exceed the available RAM on your system. The WiredTiger cache is used to store frequently accessed data and indexes in memory, so configuring an appropriate cache size based on your system’s available resources is important for optimal performance.

After making changes to the configuration, restart your MongoDB server for the new settings to take effect.