集群中五台datanode结果只起来四台，查看没起来的那台datanode日志,发现报错如下：
org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.hdfs.protocol.UnregisteredNodeException): Data node DatanodeRegistration(192.168.1.204:50010, datanodeUuid=809917ff-7b27-47d6-970e-76418779c9ec, infoPort=50075, infoSecurePort=0, ipcPort=50020, storageInfo=lv=-56;cid=CID-36266625-9883-4184-bd9a-309f3cbd60f2;nsid=2035073548;c=0) is attempting to report storage ID 809917ff-7b27-47d6-970e-76418779c9ec. Node 192.168.1.200:50010 is expected to serve this storage.
at org.apache.hadoop.hdfs.server.blockmanagement.DatanodeManager.getDatanode(DatanodeManager.java:495)
at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.processReport(BlockManager.java:1812)
at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer$1.call(NameNodeRpcServer.java:1326)
at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer$1.call(NameNodeRpcServer.java:1323)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager$BlockReportProcessingThread.processQueue(BlockManager.java:3837)
at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager$BlockReportProcessingThread.run(BlockManager.java:3816)
at org.apache.hadoop.ipc.Client.call(Client.java:1475)
at org.apache.hadoop.ipc.Client.call(Client.java:1412)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:229)
at com.sun.proxy.$Proxy15.blockReport(Unknown Source)
at org.apache.hadoop.hdfs.protocolPB.DatanodeProtocolClientSideTranslatorPB.blockReport(DatanodeProtocolClientSideTranslatorPB.java:202)
at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.blockReport(BPServiceActor.java:463)
at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.offerService(BPServiceActor.java:688)
at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.run(BPServiceActor.java:824)
at java.lang.Thread.run(Thread.java:748)
猜测是storage id出错了,应该是我备份镜像的时候，没删掉这个data。
于是找到datanode的data文件价，移去current文件夹，重新启动datanode:
hadoop-daemon.sh start datanode
正常启动了
