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https://issues.apache.org/jira/browse/HDFS-3077?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13242834#comment-13242834
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Flavio Junqueira commented on HDFS-3077:
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bq. True, though BK takes effort to interleave all of the ledgers into a single
sequential stream, while writing an index file to allow de-interleaving upon
read.
We have done this interleaving originally because the performance was affected
even with just a handful of log files (ledgers). The solution we have currently
apply to a few or tens of thousands of ledgers.
If you're concerned about read performance, we have not observed any important
reduction. About de-interleaving, we don't rearrange it or anything, if that's
what you have in mind.
> Quorum-based protocol for reading and writing edit logs
> -------------------------------------------------------
>
> Key: HDFS-3077
> URL: https://issues.apache.org/jira/browse/HDFS-3077
> Project: Hadoop HDFS
> Issue Type: New Feature
> Components: ha, name-node
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
>
> Currently, one of the weak points of the HA design is that it relies on
> shared storage such as an NFS filer for the shared edit log. One alternative
> that has been proposed is to depend on BookKeeper, a ZooKeeper subproject
> which provides a highly available replicated edit log on commodity hardware.
> This JIRA is to implement another alternative, based on a quorum commit
> protocol, integrated more tightly in HDFS and with the requirements driven
> only by HDFS's needs rather than more generic use cases. More details to
> follow.
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