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From "Suresh Srinivas (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3107) HDFS truncate
Date Tue, 20 Mar 2012 02:35:38 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3107?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13233134#comment-13233134

Suresh Srinivas commented on HDFS-3107:

bq. if a user mistakenly starts to append data to an existing large file, and discovers the
mistake, the only recourse is to recreate that file, by rewriting the contents. This is very

What if user accidentally truncates a file :-)
> HDFS truncate
> -------------
>                 Key: HDFS-3107
>                 URL: https://issues.apache.org/jira/browse/HDFS-3107
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: data-node, name-node
>            Reporter: Lei Chang
>         Attachments: HDFS_truncate_semantics_Mar15.pdf
>   Original Estimate: 1,344h
>  Remaining Estimate: 1,344h
> Systems with transaction support often need to undo changes made to the underlying storage
when a transaction is aborted. Currently HDFS does not support truncate (a standard Posix
operation) which is a reverse operation of append, which makes upper layer applications use
ugly workarounds (such as keeping track of the discarded byte range per file in a separate
metadata store, and periodically running a vacuum process to rewrite compacted files) to overcome
this limitation of HDFS.

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