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https://issues.apache.org/jira/browse/HDFS-8432?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Chris Nauroth updated HDFS-8432:
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Attachment: HDFS-8432-HDFS-Downgrade-Extended-Support.pdf
I'm attaching a brief design document and patch. Some of this discussion
originated on HDFS-5223.
> Introduce a minimum compatible layout version to allow downgrade in more
> rolling upgrade use cases.
> ---------------------------------------------------------------------------------------------------
>
> Key: HDFS-8432
> URL: https://issues.apache.org/jira/browse/HDFS-8432
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode, rolling upgrades
> Reporter: Chris Nauroth
> Assignee: Chris Nauroth
> Attachments: HDFS-8432-HDFS-Downgrade-Extended-Support.pdf
>
>
> Maintain the prior layout version during the upgrade window and reject
> attempts to use new features until after the upgrade has been finalized.
> This guarantees that the prior software version can read the fsimage and edit
> logs if the administrator decides to downgrade. This will make downgrade
> usable for the majority of NameNode layout version changes, which just
> involve introduction of new edit log operations.
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