Modify Chunk Size in a Sharded Cluster修改分片群集中的块大小

The default chunk size for a sharded cluster is 128 megabytes. 分片集群的默认区块大小为128 MB。This default chunk size works well for most deployments; however, if you notice that automatic migrations have more I/O than your hardware can handle, you may want to reduce the chunk size. 此默认块大小适用于大多数部署；但是，如果您注意到自动迁移的I/O超过了硬件的处理能力，那么您可能需要减小块大小。For automatic splits and migrations, a small chunk size leads to more rapid and frequent migrations. 对于自动拆分和迁移，较小的块大小会导致更快速、更频繁的迁移。The allowed range of the chunk size is between 1 and 1024 megabytes, inclusive.区块大小的允许范围为1到1024 MB（包括1和1024 MB）。

To modify the chunk size, use the following procedure:要修改区块大小，请使用以下步骤：

1. Connect to any mongos in the cluster using mongosh.使用mongosh连接到集群中的任何mongos。

2. Issue the following command to switch to the Config Database:发出以下命令以切换到配置数据库：

   use config

3. Issue the following command to store the global chunk size configuration value:发出以下命令以存储全局块大小配置值：

   db.settings.updateOne(
      { _id: "chunksize" },
      { $set: { _id: "chunksize", value: <sizeInMB> } },
      { upsert: true }
   )

Modifying the chunk size has several limitations:修改区块大小有几个限制：

• Automatic splitting only occurs on insert or update.自动拆分仅在插入或更新时发生。
• If you lower the chunk size, it may take time for all chunks to split to the new size.如果降低块大小，则可能需要一些时间才能将所有块拆分为新大小。
• Splits cannot be undone.拆分无法撤消。
• If you increase the chunk size, existing chunks grow only through insertion or updates until they reach the new size.如果增加块大小，现有块仅通过插入或更新来增长，直到达到新大小。
• The allowed range of the chunk size is between 1 and 1024 megabytes, inclusive.区块大小的允许范围为1到1024 MB（包括1和1024 MB）。