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From "Sanjay Radia (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3077) Quorum-based protocol for reading and writing edit logs
Date Mon, 01 Oct 2012 18:25:14 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3077?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13467051#comment-13467051
] 

Sanjay Radia commented on HDFS-3077:
------------------------------------

Section 2.10.6
* How can JN1 get new transactions (151, 152, 153) till finalization has been achieved on
a quorum JNs?
Or do you mean that finalize succeeded and all JNs created "edits-inprogress-151" and then
 "edits-inprogress-151" got deleted from JN2 and JN3 because they had no transactions in them
as described in 2.10.5?

* At the end of recovery, can we guarantee that a new open segment is created with one no-op
transaction in it? 
BTW I thought that with HDFS-1073 each segment has an initial no-op transaction (BTW did we
have a similar close-segment transaction in HDFS-1073?); did this change as part of HDFS-3077?


                
> 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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