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https://issues.apache.org/jira/browse/HDFS-3077?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13467041#comment-13467041
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Sanjay Radia commented on HDFS-3077:
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Section 2.9
The use of the term "master" can be confused with "recovery coordinator". The
master JN is the source for the journal synchronization. The section title uses
the word "recovery" - this word is also used section 2.8.
* clarify this in the section
* the journal can be sync'ed from multiple sources - shouldn't this be a list
of "Master(s)"?
* use another term: "journal-sync-master(s)" or "journal-sycn-source(s)" - I
prefer the word "source"
* Change title of the section to be "Journal Synchronization - Choosing the
Source" (or Master?).
Q. is Synchronization needed before proceeding when you have a Quorum of JNs
that have all the transaction. That is, in that case does the "acceptRecovery"
operation (section 2.8) force the last log segment in each of the JNs to be
consistently finalized? Either, way please clarify this in section 2.9.
(Clearly all unsync'ed JNs have to sync with one of the other JNs.) I think you
are using the design and code of HDFS-3092 but at times I am not sure when i
read this section.
> 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.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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