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https://issues.apache.org/jira/browse/HDFS-3979?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13466113#comment-13466113
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Lars Hofhansl commented on HDFS-3979:
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I see. Thanks Kan. So now we we have API4 and (with HDFS-744) API5.
For applications like HBase we'd like API4 as well as API5.
(API4 allows a hypothetical kill -9 of all DNs without loss of acknowledged
data, API5 allows HW failures of all data nodes - i.e. a DC outage - with loss
of acknowledged data)
> 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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