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https://issues.apache.org/jira/browse/HDFS-15059?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16995809#comment-16995809
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Kihwal Lee commented on HDFS-15059:
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bq. It's is safe because the DirectoryScanner will run soon to correct possible
missmatch.
That's not true. Once the initial full block report goes out to the namenode,
the damage is already done.
> Cache finalized replica info during datanode shutdown for fast restarting
> -------------------------------------------------------------------------
>
> Key: HDFS-15059
> URL: https://issues.apache.org/jira/browse/HDFS-15059
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: datanode
> Reporter: Yang Yun
> Assignee: Yang Yun
> Priority: Minor
> Attachments: HDFS-15059.patch
>
>
> HDFS-7928 persist the whole volume map on the disk and let the datanode read
> that file and create the volume map during startup. This significantly
> improve the datanode startup time.
> But it not works for any cases. For example, if datanode is killed, it's no
> chance to save the volume map.
> Add a shutdown hook to make sure the volume map is saved during shutdown.
> If the datanode is terminated by kill or other methods, we only reload the
> finalized replca from cache. It's is safe because the DirectoryScanner will
> run soon to correct possible missmatch.
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