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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-1117) DFS Scalability: When the namenode is restarted it consumes 80% CPU
Date Wed, 14 Mar 2007 18:30:09 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-1117?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

dhruba borthakur updated HADOOP-1117:
-------------------------------------

    Attachment: CpuPendingTransfer2.patch

pendingTranfer does not cause any replication if the replication factor has already been achieved.
Also, addStoredBlock() removes blocks from neededReplication if the replicationfactor has
already been achieved.

> DFS Scalability: When the namenode is restarted it consumes 80% CPU
> -------------------------------------------------------------------
>
>                 Key: HADOOP-1117
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1117
>             Project: Hadoop
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.12.0
>            Reporter: dhruba borthakur
>         Assigned To: dhruba borthakur
>            Priority: Blocker
>             Fix For: 0.12.1
>
>         Attachments: CpuPendingTransfer2.patch
>
>
> When the namenode is restarted, the datanodes register and each block is inserted into
neededReplication. When the namenode exists, safemode it sees starts processing neededReplication.
It picks up a block from neededReplication, sees that it has already has the required number
of replicas, and continues to the next block in neededReplication. The blocks remain in neededReplication
permanentlyhe namenode worker thread to scans this huge list of blocks once every 3 seconds.
This consumes plenty of CPU on the namenode.

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