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From "Tsz Wo Nicholas Sze (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7535) Utilize Snapshot diff report for distcp
Date Thu, 26 Feb 2015 16:16:05 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7535?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14338629#comment-14338629
] 

Tsz Wo Nicholas Sze commented on HDFS-7535:
-------------------------------------------

Thanks for working on this.  The idea is great!  Some comments on the patch:
- In DistCpSync.moveToTmpDir, why move the paths to tmp for the delete operations?
- In DistCpSync.moveToTarget, it mkdir if parent directory does not exist.  Would it be able
to preserve other attributes for the "-p" option?
- In DiffInfo.getDiffs(..), no need to create the entries array.  Just iterate over report.getDiffList().
- Please add javadoc for DiffInfo.

> Utilize Snapshot diff report for distcp
> ---------------------------------------
>
>                 Key: HDFS-7535
>                 URL: https://issues.apache.org/jira/browse/HDFS-7535
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: distcp, snapshots
>            Reporter: Jing Zhao
>            Assignee: Jing Zhao
>         Attachments: HDFS-7535.000.patch, HDFS-7535.001.patch, HDFS-7535.002.patch
>
>
> Currently HDFS snapshot diff report can identify file/directory creation, deletion, rename
and modification under a snapshottable directory. We can use the diff report for distcp between
the primary cluster and a backup cluster to avoid unnecessary data copy. This is especially
useful when there is a big directory rename happening in the primary cluster: the current
distcp cannot detect the rename op thus this rename usually leads to large amounts of real
data copy.
> More details of the approach will come in the first comment.



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