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From "Dmytro Molkov (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HDFS-1108) ability to create a file whose newly allocated blocks are automatically persisted immediately
Date Tue, 22 Jun 2010 22:35:54 GMT

     [ https://issues.apache.org/jira/browse/HDFS-1108?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Dmytro Molkov updated HDFS-1108:
--------------------------------

    Attachment: HDFS-1108.patch

This is a rather simple patch.
When we allocate new block - call persistBlocks on the file. While we do not sync the transaction
log to disk this seems to be reasonable enough, since the only problematic case is with the
machine crashing.

The test creates a file, waits for a few blocks to become available, then stops the mini cluster
without closing the file and starts it again.
The length of the file cannot be smaller than before the restart if the blocks were persisted
into log.

> 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: Dmytro Molkov
>         Attachments: HDFS-1108.patch
>
>
> 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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