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https://issues.apache.org/jira/browse/HDFS-11090?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15667949#comment-15667949
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Konstantin Shvachko commented on HDFS-11090:
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Andrew, "empty cluster" as a special case was always there. It was somewhat
tempered when DataNodes where added to SafeMode conditions. I guess even if
there are no blocks in the cluster you would at least want to wait for DN
registrations to assure you have anything to write to.
Also don't give up on {{-D}} option easy. Not knowing your scripts, but one can
safely assume that you have to format the cluster before first start, so it is
a special case in startup, which sort of extends to the first startup.
> Leave safemode immediately if all blocks have reported in
> ---------------------------------------------------------
>
> Key: HDFS-11090
> URL: https://issues.apache.org/jira/browse/HDFS-11090
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode
> Affects Versions: 2.7.3
> Reporter: Andrew Wang
> Assignee: Yiqun Lin
> Attachments: HDFS-11090.001.patch
>
>
> Startup safemode is triggered by two thresholds: % blocks reported in, and
> min # datanodes. It's extended by an interval (default 30s) until these two
> thresholds are met.
> Safemode extension is helpful when the cluster has data, and the default %
> blocks threshold (0.99) is used. It gives DNs a little extra time to report
> in and thus avoid unnecessary replication work.
> However, we can leave startup safemode early if 100% of blocks have reported
> in.
> Note that operators sometimes change the % blocks threshold to > 1 to never
> automatically leave safemode. We should maintain this behavior.
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