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https://issues.apache.org/jira/browse/HDFS-3107?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14282267#comment-14282267
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Yi Liu commented on HDFS-3107:
------------------------------
I have done some functionality tests in my cluster, and do some code review
from my point of view (I'm not very good at snapshot part, so just did some
basic review for that part :)).
+1 (non-binding) for merging into branch-2, it's good to me, except some small
nits, and I filed them in HDFS-7634 and HDFS-7638. Certainly we can file follow
ups if I find some new issues.
> 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
> Fix For: 3.0.0
>
> 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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