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From "Suresh Srinivas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5138) Support HDFS upgrade in HA
Date Mon, 27 Jan 2014 18:55:51 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5138?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13883110#comment-13883110
] 

Suresh Srinivas commented on HDFS-5138:
---------------------------------------

[~atm], please address the comments before merging to branch-2.

My main concern apart from comments on the code is, the need to have all JNs and when any
of the steps related to a JN fails, the boundary conditions that arise out of it. These issues
can result in loss of metadata and very involved, error prone recovery procedure. It also
might need the system to be restarted (say finalize fails because one of the JNs is not up).
Please look at the comments on the design and see if I understand it correctly.

> Support HDFS upgrade in HA
> --------------------------
>
>                 Key: HDFS-5138
>                 URL: https://issues.apache.org/jira/browse/HDFS-5138
>             Project: Hadoop HDFS
>          Issue Type: Bug
>    Affects Versions: 2.1.1-beta
>            Reporter: Kihwal Lee
>            Assignee: Aaron T. Myers
>            Priority: Blocker
>         Attachments: HDFS-5138.patch, HDFS-5138.patch, HDFS-5138.patch, HDFS-5138.patch,
HDFS-5138.patch, HDFS-5138.patch, HDFS-5138.patch, HDFS-5138.patch, HDFS-5138.patch, HDFS-5138.patch,
HDFS-5138.patch, hdfs-5138-branch-2.txt
>
>
> With HA enabled, NN wo't start with "-upgrade". Since there has been a layout version
change between 2.0.x and 2.1.x, starting NN in upgrade mode was necessary when deploying 2.1.x
to an existing 2.0.x cluster. But the only way to get around this was to disable HA and upgrade.

> The NN and the cluster cannot be flipped back to HA until the upgrade is finalized. If
HA is disabled only on NN for layout upgrade and HA is turned back on without involving DNs,
things will work, but finaliizeUpgrade won't work (the NN is in HA and it cannot be in upgrade
mode) and DN's upgrade snapshots won't get removed.
> We will need a different ways of doing layout upgrade and upgrade snapshot.  I am marking
this as a 2.1.1-beta blocker based on feedback from others.  If there is a reasonable workaround
that does not increase maintenance window greatly, we can lower its priority from blocker
to critical.



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