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https://issues.apache.org/jira/browse/HADOOP-11794?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15937370#comment-15937370
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Yongjun Zhang commented on HADOOP-11794:
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Had a discussion with [~atm] (thanks ATM), we now agreed on an approach that
- relax the file system checking,
- adding the doc as [~steve_l] commented, stating concat need to be supported
when the feature is turned on
- creating follow-up jiras to add unit tests and validation for ADLS and other
file systems
- for file systems that don't support getBlockLocations or concat, create
jiras to let them fail the run sooner.
Please be aware of the situation I pointed out in my last comment, that if user
enabled this feature for file systems that don't support concat, distcp may
fail in the middle of a run and make the file system into an inconsistent state.
Does that sound good to all?
Thanks.
> distcp can copy blocks in parallel
> ----------------------------------
>
> Key: HADOOP-11794
> URL: https://issues.apache.org/jira/browse/HADOOP-11794
> Project: Hadoop Common
> Issue Type: Improvement
> Components: tools/distcp
> Affects Versions: 0.21.0
> Reporter: dhruba borthakur
> Assignee: Yongjun Zhang
> Attachments: HADOOP-11794.001.patch, HADOOP-11794.002.patch,
> HADOOP-11794.003.patch, HADOOP-11794.004.patch, HADOOP-11794.005.patch,
> HADOOP-11794.006.patch, HADOOP-11794.007.patch, HADOOP-11794.008.patch,
> MAPREDUCE-2257.patch
>
>
> The minimum unit of work for a distcp task is a file. We have files that are
> greater than 1 TB with a block size of 1 GB. If we use distcp to copy these
> files, the tasks either take a long long long time or finally fails. A better
> way for distcp would be to copy all the source blocks in parallel, and then
> stich the blocks back to files at the destination via the HDFS Concat API
> (HDFS-222)
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