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https://issues.apache.org/jira/browse/HDFS-2874?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Todd Lipcon resolved HDFS-2874.
-------------------------------
Resolution: Fixed
Fix Version/s: HA branch (HDFS-1623)
Hadoop Flags: Reviewed
Committed to HA branch, thanks for the reviews, all.
> HA: edit log should log to shared dirs before local dirs
> --------------------------------------------------------
>
> Key: HDFS-2874
> URL: https://issues.apache.org/jira/browse/HDFS-2874
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: ha, name-node
> Affects Versions: HA branch (HDFS-1623)
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Priority: Critical
> Fix For: HA branch (HDFS-1623)
>
> Attachments: hdfs-2874.txt, hdfs-2874.txt, hdfs-2874.txt
>
>
> Currently, the NN logs its edits to each of its edits directories in
> sequence. This can produce the following bad sequence:
> - NN accumulates 100 edits (tx 1-100) in the buffer. Writes and syncs to
> local drive, then crashes
> - Failover occurs. SBN takes over at txid=1, since txid 1 never got writen.
> - First NN restarts. It reads up to txid 100 from its local directories. It
> is now "ahead" of the active NN with inconsistent state.
> The solution is to write to the shared edits dir, and sync that, before
> writing to any local drives.
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