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From "Aaron T. Myers (Updated) (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-3256) HDFS considers blocks under-replicated if topology script is configured with only 1 rack
Date Thu, 12 Apr 2012 17:07:20 GMT

     [ https://issues.apache.org/jira/browse/HDFS-3256?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Aaron T. Myers updated HDFS-3256:
---------------------------------

    Attachment: HDFS-3256.patch

Great point, Todd. Looks like that check wasn't quite as conservative as I'd thought.

Here's an updated patch which only calls BlockManager#processMisReplicatedBlocks if we're
becoming a multi-rack cluster AND we're already processing repl queues. This makes sense,
since if we're not already processing repl queues then we're guaranteed that processMisReplicatedBlocks
will be called later when we do start processing repl queues, triggered by leaving safemode,
becoming active, etc.
                
> HDFS considers blocks under-replicated if topology script is configured with only 1 rack
> ----------------------------------------------------------------------------------------
>
>                 Key: HDFS-3256
>                 URL: https://issues.apache.org/jira/browse/HDFS-3256
>             Project: Hadoop HDFS
>          Issue Type: Bug
>    Affects Versions: 2.0.0
>            Reporter: Aaron T. Myers
>            Assignee: Aaron T. Myers
>         Attachments: HDFS-3256.patch, HDFS-3256.patch, HDFS-3256.patch, HDFS-3256.patch
>
>
> HDFS treats the mere presence of a topology script being configured as evidence that
there are multiple racks. If there is in fact only a single rack, the NN will try to place
the blocks on at least two racks, and thus blocks will be considered to be under-replicated.

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