hadoop 2 datanode 经常自动挂掉原因

最近在VMware上部署了Hadoop2的集群，datanode启动后经常自动就挂掉了，从网上搜到了原因，在这里记一下。

使用bin/hadoop dfsadmin -report查看系统状态

[root@crxy1 hadoop]# bin/hadoop dfsadmin -report 

Configured Capacity: 0 (0 B)

Present Capacity: 0 (0 B)

DFS Remaining: 0 (0 B)

DFS Used: 0 (0 B)

DFS Used%: NaN%

Under replicated blocks: 0

Blocks with corrupt replicas: 0

Missing blocks: 0

-------------------------------------------------

Datanodes available: 0 (0 total, 0 dead)

在datanode上查看日志，报如下错：

java.io.IOException: Incompatible clusterIDs in /usr/local/hadoop/tmp/dfs/data: namenode clusterID = CID-9cf35cc0-1da5-4e44-9770-b0d3911f9426; datanode clusterID = CID-18bf8735-ef35-4fb3-be4f-62258dc5aa09
at org.apache.hadoop.hdfs.server.datanode.DataStorage.doTransition(DataStorage.java:477)
at org.apache.hadoop.hdfs.server.datanode.DataStorage.recoverTransitionRead(DataStorage.java:226)
at org.apache.hadoop.hdfs.server.datanode.DataStorage.recoverTransitionRead(DataStorage.java:254)
at org.apache.hadoop.hdfs.server.datanode.DataNode.initStorage(DataNode.java:974)
at org.apache.hadoop.hdfs.server.datanode.DataNode.initBlockPool(DataNode.java:945)
at org.apache.hadoop.hdfs.server.datanode.BPOfferService.verifyAndSetNamespaceInfo(BPOfferService.java:278)
at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.connectToNNAndHandshake(BPServiceActor.java:220)
at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.run(BPServiceActor.java:816)
at java.lang.Thread.run(Thread.java:745)

clusterIDs 与namenode的不一致，是因为我多次格式化了namenode，导致namenode的clusterIDs 与datanode上的不一致，

解决办法:
1、在hdfs-site.xml配置文件中，配置了dfs.namenode.name.dir，在master中,该配置的目录下有个current文件夹，里面有个VERSION文件,内容如下:
#Thu Mar 13 10:51:23 CST 2014
namespaceID=1615021223
clusterID=CID-8e201022-6faa-440a-b61c-290e4ccfb006
cTime=0
storageType=NAME_NODE
blockpoolID=BP-1257313099-10.10.208.38-1394679083528
layoutVersion=-40
2、在core-site.xml配置文件中，配置了hadoop.tmp.dir（我的为/usr/local/hadoop/tmp/dfs/data/current/），在slave中,该配置的目录下有个dfs/data/current目录，里面也有一个VERSION文件，内容
#Wed Mar 12 17:23:04 CST 2014
storageID=DS-414973036-10.10.208.54-50010-1394616184818
clusterID=clustername
cTime=0
storageType=DATA_NODE
layoutVersion=-40
3、一目了然，两个内容不一样，导致的。删除slave中的错误内容，重启，搞定！

参考资料:http://blog.csdn.net/wodeyuer125/article/details/21666937
参考资料:http://blog.csdn.net/wanghai__/article/details/5752199

使用bin/hadoop dfsadmin -report查看系统状态

[root@crxy1 hadoop]# bin/hadoop dfsadmin -report 

Configured Capacity: 0 (0 B)

Present Capacity: 0 (0 B)

DFS Remaining: 0 (0 B)

DFS Used: 0 (0 B)

DFS Used%: NaN%

Under replicated blocks: 0

Blocks with corrupt replicas: 0

Missing blocks: 0

-------------------------------------------------

Datanodes available: 0 (0 total, 0 dead)