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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1108) ability to create a file whose newly allocated blocks are automatically persisted immediately
Date Fri, 23 Apr 2010 23:38:50 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1108?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12860421#action_12860421
] 

dhruba borthakur commented on HDFS-1108:
----------------------------------------

This feature is needed to make HBase work seamlessly with NameNode HA (HDFS-976). Suppose
a region server created a new file and has written some data to it and then the NN failed-over
to the hot-standby. The client should be able to continue writing data to the same file that
is now being served by the new NameNode.

> ability to create a file whose newly allocated blocks are automatically persisted immediately
> ---------------------------------------------------------------------------------------------
>
>                 Key: HDFS-1108
>                 URL: https://issues.apache.org/jira/browse/HDFS-1108
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>
> The current HDFS design says that newly allocated blocks for a file are not persisted
in the NN transaction log when the block is allocated. Instead, a hflush() or a close() on
the file persists the blocks into the transaction log. It would be nice if we can immediately
persist newly allocated blocks (as soon as they are allocated) for specific files.

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