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https://issues.apache.org/jira/browse/HDFS-270?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12992645#comment-12992645
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Hairong Kuang commented on HDFS-270:
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Matt, thanks so much for sharing the patch to HDFS-1445. I will review it.
Cutting the time from 8 min to 8 sec is so impressive! Job well done!
> DFS Upgrade should process dfs.data.dirs in parallel
> ----------------------------------------------------
>
> Key: HDFS-270
> URL: https://issues.apache.org/jira/browse/HDFS-270
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: data-node
> Affects Versions: 0.20.2
> Reporter: Stu Hood
> Assignee: Hairong Kuang
>
> I just upgraded from 0.14.2 to 0.15.0, and things went very smoothly, if a
> little slowly.
> The main reason the upgrade took so long was the block upgrades on the
> datanodes. Each of our datanodes has 3 drives listed for the dfs.data.dir
> parameter. From looking at the logs, it is fairly clear that the upgrade
> procedure does not attempt to upgrade all listed dfs.data.dir's in parallel.
> I think even if all of your dfs.data.dir's are on the same physical device,
> there would still be an advantage to performing the upgrade process in
> parallel. The less downtime, the better: especially if it is potentially 20
> minutes versus 60 minutes.
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