Database Manual / Sharding / Administration

Add Shards to a Cluster将分片添加到集群

You add shards to a sharded cluster after you create the cluster or any time that you need to add capacity to the cluster. 您可以在创建集群后或需要向集群添加容量时向分片集群添加分片。If you have not created a sharded cluster, see Deploy a Self-Managed Sharded Cluster.如果您尚未创建分片集群，请参阅部署自我管理的分片集群。

All shards must be replica sets.所有分片都必须是副本集。

Considerations注意事项

Balancing平衡

When you add a shard to a sharded cluster, you affect the balance of chunks among the shards of a cluster for all existing sharded collections. The balancer will begin migrating chunks so that the cluster will achieve balance. 当你向分片集群添加一个分片时，你会影响所有现有分片集合的集群分片之间的块平衡。平衡器将开始迁移块，以便集群实现平衡。See Balancer Internals for more information.有关更多信息，请参阅平衡器内部。

Capacity Planning容量规划

When adding a shard to a cluster, always ensure that the cluster has enough capacity to support the migration required for balancing the cluster without affecting legitimate production traffic.在向集群添加分片时，始终确保集群有足够的容量来支持平衡集群所需的迁移，而不会影响合法的生产流量。

DDL OperationsDDL操作

If you add a shard while your cluster executes a DDL operation (operation that modifies a collection such as reshardCollection), the operation that adds a shard only executes after the concurrent DDL operation finishes.如果在集群执行DDL操作（修改reshardCollection等集合的操作）时添加分片，则添加分片的操作仅在并发DDL操作完成后执行。

Add a Shard to a Cluster将分片添加到集群

You interact with a sharded cluster by connecting to a mongos instance.通过连接到mongos实例，您可以与分片集群进行交互。

  1. In mongosh, connect to the mongos instance. 在mongosh中，连接到mongos实例。For example, if a mongos is accessible at mongos0.example.net on port 27017, issue the following command:例如，如果mongos可以在端口27017的mongos0.example.net上访问，请发出以下命令：

    mongosh --host mongos0.example.net --port 27017

  2. Add a shard replica set to the cluster using the sh.addShard() method, as shown in the example below. 使用sh.addShard()方法将分片副本集添加到集群中，如下例所示。Issue sh.addShard() separately for each shard. Specify the name of the replica set and a member of the set.为每个分片分别发出sh.addShard()。指定副本集的名称和该集的一个成员。

    Note

    Optional可选的

    You can instead use the addShard database command, which lets you specify a name and maximum size for the shard. If you do not specify these, MongoDB automatically assigns a name and maximum size. To use the database command, see addShard.您可以使用addShard数据库命令，该命令允许您指定分片的名称和最大大小。如果你不指定这些，MongoDB会自动分配一个名称和最大大小。要使用数据库命令，请参阅addShard。

    The following example illustrates adding a shard with sh.addShard():以下示例说明了如何使用sh.addShard()添加分片：

    To add a shard replica set named rs1 with a member running on port 27018 on mongodb0.example.net, issue the following command:要添加一个名为rs1的分片副本集，其成员在mongodb0.example.net的27018端口上运行，请发出以下命令：

    sh.addShard( "rs1/mongodb0.example.net:27018" )

    Note

    It might take some time for chunks to migrate to the new shard.块迁移到新分片可能需要一些时间。