could only be replicated to 0 nodes instead of minReplication (=1). There are 4 datanode(s) running

http://stackoverflow.com/questions/34245682/could-only-be-replicated-to-0-nodes-instead-of-minreplication-1-there-are-4

还有一种可能是那台服务器连接到hdfs的连接数太多，仅供参考。