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From "Jing Zhao (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3689) Add support for variable length block
Date Fri, 08 Aug 2014 22:36:12 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3689?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14091390#comment-14091390

Jing Zhao commented on HDFS-3689:

Looks like we do not have a lot of dependency on the fixed block length. I've found the following
several places related to the preferred block size of the file:
# concat. Currently concat has very strict preconditions including all the corresponding files
have the same preferred block size and all the files (except the last one) should consist
of full block.
# writing data. DFSOutputstream/DataStreamer allocates a new block after writing a full block.
# append. New data is always appended to the end of the last block unless it's just on the
block boundary.
# addBlock. In the addBlock RPC, the client specifies the previous block as null to indicate
that this is the first new block for an append operation right at the block boundary. NameNode
calls {{analyzeFileState}} to verify this logic.

> Add support for variable length block
> -------------------------------------
>                 Key: HDFS-3689
>                 URL: https://issues.apache.org/jira/browse/HDFS-3689
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: datanode, hdfs-client, namenode
>    Affects Versions: 3.0.0
>            Reporter: Suresh Srinivas
>            Assignee: Suresh Srinivas
> Currently HDFS supports fixed length blocks. Supporting variable length block will allow
new use cases and features to be built on top of HDFS. 

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