HDFS replication factor

[李立伟]

Hi:
      It's my understanding that HDFS write  operation is not considered
completd until all of the replicas have been successfully written.If so,
does the replication factor affect the write latency? the mapreduce\spark
task will be affected?
      is there the way to set HDFS write the first replica synchronously
and return ,the others in an asynchronous.
      Thanks in advance.