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From "Suresh Srinivas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5138) Support HDFS upgrade in HA
Date Wed, 15 Jan 2014 22:02:40 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5138?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13872657#comment-13872657
] 

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

[~atm], I am looking at this patch. As I see this, I feel this change should include design
details. Some questions that come to mind:
# In documentation you say "    [[2]] Both NNs must be started with the <<<'-upgrade'>>>
flag." Does this mean both the namenodes should be available during upgrade or does it just
mean that namenodes must be started with -upgrade. One of the namenode can first upgrade (and
possibly be finalized) and later  second NN can be upgraded?
# When active namenode is performing shared edits upgrade, if it fails, does fail over occur
to the standby and  does the new active resume the upgrade? Same question for finalize and
rollback.
# In documentation "The operator should run the roll back command on one of the NN boxes,...",
could have issues related to which NN is chosen. It must be on the one where upgrade has been
previously done right?
# Given the rollback procedure, where bootstrapStandby muste be done on one of the NNs, why
not just upgrade a single namenode (without worrying about two namenodes racing to upgrade
etc.) and just follow the same procedure as rollback to simplify this?

> 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
>
>
> 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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