hdfs 的存储空间扩展

问题：之前集群上每个节点的的大小为50G， 但是硬盘容量是160G的， 不明白为什么才50个G；

后来发现是因为dfs.data.dir设置的问题，该目录下挂载的磁盘空间的大小就会作为该节点的容量。。

所以想到了挂两个目录，一个在 / 下面，一个在 /home下面，因为我的集群上这两个目录是挂在不同分区上的

但是随之而来的问题就是：

/************************************************************
STARTUP_MSG: Starting DataNode
STARTUP_MSG:   host = cdfsrv6.mit.edu/18.77.0.180
STARTUP_MSG:   args = []
STARTUP_MSG:   version = 0.19.2-dev
STARTUP_MSG:   build = http://svn.apache.org/repos/asf/hadoop/core/tags/release-0.19.1 -r 748415; compiled by 'wart' on Mon Mar 23 15:21:37 PDT 2009
************************************************************/
2010-03-30 16:46:18,456 ERROR datanode.DataNode (DataNode.java:main(1331)) - org.apache.hadoop.hdfs.server.common.InconsistentFSStateException: Directory /export/06a/hadoop/data is in an inconsistent state: has incompatible storage Id.
        at org.apache.hadoop.hdfs.server.datanode.DataStorage.getFields(DataStorage.java:183)
        at org.apache.hadoop.hdfs.server.common.Storage$StorageDirectory.read(Storage.java:227)
        at org.apache.hadoop.hdfs.server.common.Storage$StorageDirectory.read(Storage.java:216)
        at org.apache.hadoop.hdfs.server.datanode.DataStorage.doTransition(DataStorage.java:228)
        at org.apache.hadoop.hdfs.server.datanode.DataStorage.recoverTransitionRead(DataStorage.java:148)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.startDataNode(DataNode.java:291)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.<init>(DataNode.java:209)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.makeInstance(DataNode.java:1242)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.instantiateDataNode(DataNode.java:1197)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.createDataNode(DataNode.java:1205)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.main(DataNode.java:1327)

This is caused if one of the data directories gets reformatted. This causes the VERSION file (i.e., /path/to/hadoop/data/current/VERSION) to get regenerated. If there are multiple data directories, and at least one has a different VERSION file, you will get this message.

 Solution

Take the following actions:

1. Verify there is no datanode java process on the node currently running.
2. Create a backup of all the VERSION files.
3. Copy one of the VERSION files into all the data directories in the correct place ($PREFIX/current/VERSION).
4. Start the data node. If the error does not go away, contact osg-hadoop support.

参考文献：https://twiki.grid.iu.edu/bin/view/Storage/HadoopDebug#Incompatible_Storage_IDs_on_the