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https://issues.apache.org/jira/browse/HADOOP-11794?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Yongjun Zhang updated HADOOP-11794:
-----------------------------------
Release Note:
If a positive value is passed to command line switch -blocksperchunk, files
with more blocks than this value will be split into chunks of
`<blocksperchunk>` blocks to be transferred in parallel, and reassembled on the
destination. By default, `<blocksperchunk>` is 0 and the files will be
transmitted in their entirety without splitting. This switch is only applicable
when both the source file system supports getBlockLocations and target supports
concat.
was:
If a positive value is passed to command line switch -blocksperchunk, files
with more blocks than this value will be split into chunks of
`<blocksperchunk>` blocks to be transferred in parallel, and reassembled on the
destination. By default, `<blocksperchunk>` is 0 and the files will be
transmitted in their entirety without splitting. This switch is only applicable
when both the source and target are DistributedFileSystem.
> 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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