我有以下配置的cassandra群集设置gurations:-
节点：5
数据中心：dc1
复制因子：3
一致性： LOCAL_QUORUM 在表上执行批处理语句时出现以下异常。

com.datastax.driver.core.exceptions.WriteTimeoutException: Cassandra timeout during 
write query at consistency LOCAL_QUORUM (3 replica were required 
but only 2 acknowledged the write).

当一致性是本地\u仲裁（2）时，为什么它说需要3个复制副本？