Modify Range Size in a Sharded Cluster

The default range size for a sharded cluster is 128 megabytes. This default range size works well for most deployments; however, if you notice that automatic migrations use more I/O than your hardware can handle, you may want to reduce the range size. A small range size leads to more rapid and frequent migrations. The allowed size is between 1 and 1024 megabytes, inclusive.

To modify the range size, use the following procedure:

Connect to any mongos in the cluster using mongosh.
Issue the following command to switch to the Config Database:
```
use config
```
Issue the following command to store the global range size configuration value:
```
db.settings.updateOne(
   { _id: "chunksize" },
   { $set: { _id: "chunksize", value: <sizeInMB> } },
   { upsert: true }
)
```

The allowed range size is between 1 and 1024 megabytes, inclusive.

To set the chunk size for a specific collection, see configureCollectionBalancing.

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