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https://issues.apache.org/jira/browse/HDFS-3077?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13472575#comment-13472575
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Sanjay Radia commented on HDFS-3077:
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I propose we do the following
# Recover all transactions. We do this in the same fashion as ZAB rather then
the way you suggested "the NN can run the recovery process for each of these
earlier segments individually". Note this requires two changes:
** The protocol message contents change - the response to phase 1 is highest
txid and not highest segment's txid. The JN recovers all previous transactions
from another JN.
** When a JN joins an existing writer it first syncs previous segments.
# 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 am fine doing this in 2 separate jiras after the merge if you prefer. You
have already volunteered to work on (1). Suresh or I can work on (2).
> 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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