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From "Jonathan Hsieh (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2576) Namenode should have a favored nodes hint to enable clients to have control over block placement.
Date Wed, 27 Feb 2013 20:59:15 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2576?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13588742#comment-13588742
] 

Jonathan Hsieh commented on HDFS-2576:
--------------------------------------

Would the making this persistent be addressed here or as a follow on issue?

>From a design point of view would it be possible to just add an attribute or flag on hdfs
files or directories that specify an block affinity group?  This would seem cheaper than an
alternative that specifies specific favored dn's lists for block replicas.  This would seem
more robust than something specified only at file creation time, and more managable in the
long term if data nodes membership changes over time.

                
> Namenode should have a favored nodes hint to enable clients to have control over block
placement.
> -------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-2576
>                 URL: https://issues.apache.org/jira/browse/HDFS-2576
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>            Reporter: Pritam Damania
>         Attachments: hdfs-2576-1.txt
>
>
> Sometimes Clients like HBase are required to dynamically compute the datanodes it wishes
to place the blocks for a file for higher level of locality. For this purpose there is a need
of a way to give the Namenode a hint in terms of a favoredNodes parameter about the locations
where the client wants to put each block. The proposed solution is a favored nodes parameter
in the addBlock() method and in the create() file method to enable the clients to give the
hints to the NameNode about the locations of each replica of the block. Note that this would
be just a hint and finally the NameNode would look at disk usage, datanode load etc. and decide
whether it can respect the hints or not.

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