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https://issues.apache.org/jira/browse/HDFS-6087?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13946968#comment-13946968
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Konstantin Shvachko commented on HDFS-6087:
-------------------------------------------

Guo, could you please clarify. 
Are you proposing a new design for pipeline handling or just want to add 
truncate?
New pipeline handling is probably going to be hard, while adding truncate could 
be simpler.
If it is truncate you want, do you have any different requirements for APIs or 
semantics from those laid out under HDFS-3107?

> Unify HDFS write/append/truncate
> --------------------------------
>
>                 Key: HDFS-6087
>                 URL: https://issues.apache.org/jira/browse/HDFS-6087
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: hdfs-client
>            Reporter: Guo Ruijing
>         Attachments: HDFS Design Proposal.pdf, HDFS Design Proposal_3_14.pdf
>
>
> In existing implementation, HDFS file can be appended and HDFS block can be 
> reopened for append. This design will introduce complexity including lease 
> recovery. If we design HDFS block as immutable, it will be very simple for 
> append & truncate. The idea is that HDFS block is immutable if the block is 
> committed to namenode. If the block is not committed to namenode, it is HDFS 
> client’s responsibility to re-added with new block ID.



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