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https://issues.apache.org/jira/browse/HDFS-3077?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13473667#comment-13473667
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Sanjay Radia commented on HDFS-3077:
------------------------------------
{quote}
bq. Lets merge the newEpoch and prepareRecovery. Given that this works for ZAB
I still fail to see why it cannot work for us. I think because of (1), merging
the two steps will no longer be an issue.
I still don't understand why this is better and not just different. If you and
Suresh want to make the change, it's OK by me, but I expect that you will
re-run the same validation before committing (eg run the randomized fault test
a few hundred thousand times). This testing found a bunch of errors in the
design before, so any chance to the design should go through the same test
regimen to make sure we aren't missing some subtlety.
{quote}
Okay, I assume that the tests are also in the branch.
Have filed HDFS-4028 for this.
> 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
> Fix For: QuorumJournalManager (HDFS-3077)
>
> Attachments: hdfs-3077-partial.txt, hdfs-3077-test-merge.txt,
> hdfs-3077.txt, hdfs-3077.txt, hdfs-3077.txt, hdfs-3077.txt, hdfs-3077.txt,
> hdfs-3077.txt, hdfs-3077.txt, qjournal-design.pdf, qjournal-design.pdf,
> qjournal-design.pdf, qjournal-design.pdf, qjournal-design.pdf,
> qjournal-design.pdf, qjournal-design.tex, qjournal-design.tex
>
>
> 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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