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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] Created: (HDFS-970) FSImage writing should always fsync before close
Date Thu, 11 Feb 2010 23:38:28 GMT
FSImage writing should always fsync before close

                 Key: HDFS-970
                 URL: https://issues.apache.org/jira/browse/HDFS-970
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: name-node
    Affects Versions: 0.20.1, 0.21.0, 0.22.0
            Reporter: Todd Lipcon
            Assignee: Todd Lipcon
            Priority: Critical

Without an fsync, it's common that filesystems will delay the writing of metadata to the journal
until all of the data blocks have been flushed. If the system crashes while the dirty pages
haven't been flushed, the file is left in an indeterminate state. In some FSs (eg ext4) this
will result in a 0-length file. In others (eg XFS) it will result in the correct length but
any number of data blocks getting zeroed. Calling FileChannel.force before closing the FSImage
prevents this issue.

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