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https://issues.apache.org/jira/browse/HDFS-3107?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14273144#comment-14273144
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Konstantin Shvachko commented on HDFS-3107:
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[~wheat9] do you have comments or suggestions on the patch? Or do you have 
anybody in particular in mind to return from vacation? I mean we cannot wait 
for everybody as the Hadoop community is pretty big - there is always somebody 
on vacation.
I don't think we are rushing here. The patch is sitting here from September. 
People expressed desire to have the snapshot support implemented before 
committing the feature, which is now also done under HDFS-7056. And went 
through a series of good review rounds by Jing, Collin, Cos, which improved the 
implementation substantially. Byron independently tested the feature on a 
cluster with and without snapshots.

So let's plan to finally commit both issues eod tomorrow Monday. If there are 
no more comments.

> HDFS truncate
> -------------
>
>                 Key: HDFS-3107
>                 URL: https://issues.apache.org/jira/browse/HDFS-3107
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: datanode, namenode
>            Reporter: Lei Chang
>            Assignee: Plamen Jeliazkov
>         Attachments: HDFS-3107-13.patch, HDFS-3107-14.patch, 
> HDFS-3107-15.patch, HDFS-3107-HDFS-7056-combined.patch, HDFS-3107.008.patch, 
> HDFS-3107.patch, HDFS-3107.patch, HDFS-3107.patch, HDFS-3107.patch, 
> HDFS-3107.patch, HDFS-3107.patch, HDFS-3107.patch, HDFS-3107.patch, 
> HDFS-3107.patch, HDFS-3107.patch, HDFS-3107.patch, HDFS_truncate.pdf, 
> HDFS_truncate.pdf, HDFS_truncate.pdf, HDFS_truncate_semantics_Mar15.pdf, 
> HDFS_truncate_semantics_Mar21.pdf, editsStored, editsStored.xml
>
>   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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