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Merge pull request #21523 from MikuSugar/patch-1

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Update replication.md
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docs/zh/engines/table-engines/mergetree-family/replication.md
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如果配置文件中没有设置 ZooKeeper ，则无法创建复制表，并且任何现有的复制表都将变为只读。
`SELECT` 查询并不需要借助 ZooKeeper ，复本并不影响 `SELECT` 的性能，查询复制表与非复制表速度是一样的。查询分布式表时，ClickHouse的处理方式可通过设置 [max_replica_delay_for_distributed_queries](../../../operations/settings/settings.md#settings-max_replica_delay_for_distributed_queries) 和 [fallback_to_stale_replicas_for_distributed_queries](../../../operations/settings/settings.md) 修改。
`SELECT` 查询并不需要借助 ZooKeeper ，副本并不影响 `SELECT` 的性能，查询复制表与非复制表速度是一样的。查询分布式表时，ClickHouse的处理方式可通过设置 [max_replica_delay_for_distributed_queries](../../../operations/settings/settings.md#settings-max_replica_delay_for_distributed_queries) 和 [fallback_to_stale_replicas_for_distributed_queries](../../../operations/settings/settings.md) 修改。
对于每个 `INSERT` 语句，会通过几个事务将十来个记录添加到 ZooKeeper。（确切地说，这是针对每个插入的数据块; 每个 INSERT 语句的每 `max_insert_block_size = 1048576` 行和最后剩余的都各算作一个块。）相比非复制表，写 zk 会导致 `INSERT` 的延迟略长一些。但只要你按照建议每秒不超过一个 `INSERT` 地批量插入数据，不会有任何问题。一个 ZooKeeper 集群能给整个 ClickHouse 集群支撑协调每秒几百个 `INSERT`。数据插入的吞吐量（每秒的行数）可以跟不用复制的数据一样高。