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https://issues.apache.org/jira/browse/HDFS-3154?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13239847#comment-13239847
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Tsz Wo (Nicholas), SZE commented on HDFS-3154:
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> Caching has nothing to do with whether files are immutable. ...
Do you think that caching would be more efficient if the files are immutable?
> Add a notion of immutable/mutable files
> ---------------------------------------
>
> Key: HDFS-3154
> URL: https://issues.apache.org/jira/browse/HDFS-3154
> Project: Hadoop HDFS
> Issue Type: New Feature
> Components: name-node
> Reporter: Tsz Wo (Nicholas), SZE
> Assignee: Tsz Wo (Nicholas), SZE
>
> The notion of immutable file is useful since it lets the system and tools
> optimize certain things as discussed in [this email
> thread|http://mail-archives.apache.org/mod_mbox/hadoop-hdfs-dev/201203.mbox/%3CCAPn_vTuZomPmBTypP8_1xTr49Sj0fy7Mjhik4DbcAA+BLH53=g...@mail.gmail.com%3E].
> Also, many applications require only immutable files. Here is a proposal:
> - Immutable files means that the file content is immutable. Operations such
> as append and truncate that change the file content are not allowed to act on
> immutable files. However, the meta data such as replication and permission
> of an immutable file can be updated. Immutable files can also be deleted or
> renamed.
> - Users have to pass immutable/mutable as a flag in file creation. This is
> an unmodifiable property of the created file.
> - If users want to change the data in an immutable file, the file could be
> copied to another file which is created as mutable.
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