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https://issues.apache.org/jira/browse/HDFS-5138?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13864509#comment-13864509
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Aaron T. Myers commented on HDFS-5138:
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Thanks a lot for the comments, Todd and Suresh. I've got some obligations
during the first part of today but will try to get back to you later today or
tomorrow.
Suresh - as regards to a design doc, I could potentially write up a small one
if you really think it's necessary, but there really aren't all that many
subtle points here, and hopefully by answering the (very good!) questions
you've raised everything will become much clearer. The core of the patch isn't
even all that large - there's a ton of plumbing of new RPCs, etc. that make it
look more complex than it is. One of the goals I had one producing it was to
leave the existing non-HA upgrade system as untouched as possible, to reduce
the possibility of regressions so we can put this in a 2.x update ASAP.
> 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
>
>
> 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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