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From "Harsh J (Updated) (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-2547) ReplicationTargetChooser has incorrect block placement comments
Date Fri, 11 Nov 2011 12:16:52 GMT

     [ https://issues.apache.org/jira/browse/HDFS-2547?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Harsh J updated HDFS-2547:
--------------------------

      Description: 
{code}
/** The class is responsible for choosing the desired number of targets
 * for placing block replicas.
 * The replica placement strategy is that if the writer is on a datanode,
 * the 1st replica is placed on the local machine, 
 * otherwise a random datanode. The 2nd replica is placed on a datanode
 * that is on a different rack. The 3rd replica is placed on a datanode
 * which is on the same rack as the **first replca**.
 */
{code}

That should read "second replica". The test cases confirm that this is the behavior, as well
as the docs.

  was:
bq. For the common case, when the replication factor is three, HDFS's placement policy is
to put one replica on one node in the local rack, another on a node in a different (remote)
rack, and the last on a different node in the same *remote* rack.

Should actually be: "and the last on a different node in the same *local* rack."

    Fix Version/s:     (was: 0.24.0)
                   0.20.206.0
          Summary: ReplicationTargetChooser has incorrect block placement comments  (was:
Design doc is wrong about default block placement policy.)

Updating title/topic for 0.20
                
> ReplicationTargetChooser has incorrect block placement comments
> ---------------------------------------------------------------
>
>                 Key: HDFS-2547
>                 URL: https://issues.apache.org/jira/browse/HDFS-2547
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: name-node
>    Affects Versions: 0.20.1
>            Reporter: Harsh J
>            Assignee: Harsh J
>            Priority: Trivial
>             Fix For: 0.20.206.0
>
>         Attachments: HDFS-2547.patch
>
>
> {code}
> /** The class is responsible for choosing the desired number of targets
>  * for placing block replicas.
>  * The replica placement strategy is that if the writer is on a datanode,
>  * the 1st replica is placed on the local machine, 
>  * otherwise a random datanode. The 2nd replica is placed on a datanode
>  * that is on a different rack. The 3rd replica is placed on a datanode
>  * which is on the same rack as the **first replca**.
>  */
> {code}
> That should read "second replica". The test cases confirm that this is the behavior,
as well as the docs.

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