1. 我的虚拟机放在阿里云上， create方法失败，mkdirs和cat却成功

2. 使用shell, -put 可以成功写入文件

3. 我在本机的VMWare上部署了一套，按照一样的方式，create方法可以成功

4. 阿里云上我开了8020，50070端口，后来乱试又开了8021, 50010端口

我截取异常栈上的一些我认为重要的错误信息：

17/09/18 10:19:20 INFO hdfs.DFSClient: Exception in createBlockOutputStream

java.net.ConnectException: Connection timed out: no further information

at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)

......

17/09/18 10:19:20 WARN hdfs.DFSClient: Abandoning BP-2124473397-172.17.27.58-1505697429586:blk_1073741829_1005

17/09/18 10:19:20 WARN hdfs.DFSClient: Excluding datanode DatanodeInfoWithStorage[172.17.27.58:50010,DS-1b16be95-7c4d-4b75-a4f5-76526271e147,DISK]

17/09/18 10:19:20 WARN hdfs.DFSClient: DataStreamer Exception

org.apache.hadoop.ipc.RemoteException(java.io.IOException): File /hdfsapi/test/a.txt could only be replicated to 0 nodes instead of minReplication (=1).  There are 1 datanode(s) running and 1 node(s) are excluded in this operation.

......