jps
hadoop namenode -format
dfs directory : /home/hadoop/dfs
- --data
- --current/VERSION
-
#Wed Jul 30 20:41:03 CST 2014 storageID=DS-ab96ad90-7352-4cd5-a0de-7308c8a358ff clusterID=CID-aa2d4761-974b-4451-8858-bbbcf82e1fd4 cTime=0 datanodeUuid=a3356a09-780c-43e8-a721-45aecf9bdb96 storageType=DATA_NODE layoutVersion=-55
- --name
- --/current/VERSION
-
#Wed Jul 30 20:39:00 CST 2014 namespaceID=895092439 clusterID=CID-aa2d4761-974b-4451-8858-bbbcf82e1fd4 cTime=0 storageType=NAME_NODE blockpoolID=BP-152997847-127.0.0.1-1406723940846 layoutVersion=-56
-
Block Pool A Block Pool is a set of blocks that belong to a single namespace.
Datanodes store blocks for all the block pools in the cluster.
It is managed independently of other block pools.
This allows a namespace to generate Block IDs for new blocks without the need for coordination with the other namespaces.
The failure of a Namenode does not prevent the datanode from serving other Namenodes in the cluster. A Namespace and its block pool together are called Namespace Volume.
It is a self-contained unit of management. When a Namenode/namespace is deleted,
the corresponding block pool at the datanodes is deleted. Each namespace volume is upgraded as a unit, during cluster upgrade. ClusterID A new identifier ClusterID is added to identify all the nodes in the cluster. When a Namenode is formatted,
this identifier is provided or auto generated. This ID should be used for formatting the other Namenodes into the cluster.