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https://issues.apache.org/jira/browse/HDFS-3979?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13469978#comment-13469978
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Luke Lu commented on HDFS-3979:
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bq. Why API4 is needed for HBase?
Many configuration management system (simplest: pdsh -a hadoop-daemon.sh stop
datanode) shutdown/restart HDFS by kill -9 datanodes in parallel. Having to
acquiesce any OLTP like workload is error prone. How about a simple ops error:
pdsh -a killall -9 java to the wrong window (hence the wrong cluster). IMO,
API4 is not robust enough for HBase. Unless the performance difference is huge
(> 20% for hflush), which I doubt, it's not worth the risk, again IMO.
> Fix hsync and hflush semantics.
> -------------------------------
>
> Key: HDFS-3979
> URL: https://issues.apache.org/jira/browse/HDFS-3979
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: data-node, hdfs client
> Affects Versions: 0.22.0, 0.23.0, 2.0.0-alpha
> Reporter: Lars Hofhansl
> Assignee: Lars Hofhansl
> Attachments: hdfs-3979-sketch.txt, hdfs-3979-v2.txt
>
>
> See discussion in HDFS-744. The actual sync/flush operation in BlockReceiver
> is not on a synchronous path from the DFSClient, hence it is possible that a
> DN loses data that it has already acknowledged as persisted to a client.
> Edit: Spelling.
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