jps
hadoop namenode -format
dfs directory : /home/hadoop/dfs
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--data
- --current/VERSION
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#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
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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.
