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https://issues.apache.org/jira/browse/HDFS-4516?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13604963#comment-13604963
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Han Xiao commented on HDFS-4516:
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Hi Uma.
For the first method. There is also problem that the datanode has written the
data, but yet not reported to the NN. This will mislead the client that no data
for the file even synced, whick broke the defination of sync.
Second method seems ok althgh a performace loss, however, the frequence is low
and then affect is ok.
> Client crash after block allocation and NN switch before lease recovery for
> the same file can cause readers to fail forever
> ---------------------------------------------------------------------------------------------------------------------------
>
> Key: HDFS-4516
> URL: https://issues.apache.org/jira/browse/HDFS-4516
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 3.0.0, 2.0.3-alpha
> Reporter: Uma Maheswara Rao G
> Priority: Critical
>
> If client crashes just after allocating block( blocks not yet created in DNs)
> and NN also switched after this, then new Namenode will not know about locs.
> Further details will be in comment.
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