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https://issues.apache.org/jira/browse/HDFS-2731?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13177486#comment-13177486
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Eli Collins commented on HDFS-2731:
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Wrt #1, if we get the image from the NN and the edits from the shared dir, are
we sure they'll always match, eg what if we're rolling at the same time (the
other NN could be primary and active)? I was thinking asking for both from the
primary would mean we always get matched sets and therefore don't need to worry
about races.
Wrt #2, yea, I thinking we should be explicit (don't have to worry about eg the
shared dir being populated by neither NN having populated name dirs, which we
know won't be the case if the other is active), but on 2nd thought I think your
suggestion is better.
> Autopopulate standby name dirs if they're empty
> -----------------------------------------------
>
> Key: HDFS-2731
> URL: https://issues.apache.org/jira/browse/HDFS-2731
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: ha
> Affects Versions: HA branch (HDFS-1623)
> Reporter: Eli Collins
> Assignee: Eli Collins
>
> To setup a SBN we currently format the primary then manually copy the name
> dirs to the SBN. The SBN should do this automatically. Specifically, on NN
> startup, if HA with a shared edits dir is configured and populated, if the
> SBN has empty name dirs it should downloads the image and log from the
> primary (as an optimization it could copy the logs from the shared dir). If
> the other NN is still in standby then it should fail to start as it does
> currently.
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