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https://issues.apache.org/jira/browse/HDFS-14821?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Stephen O'Donnell updated HDFS-14821:
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Fix Version/s: 3.3.0
Status: Patch Available (was: Open)
> Make HDFS-14617 (fsimage sub-sections) off by default
> -----------------------------------------------------
>
> Key: HDFS-14821
> URL: https://issues.apache.org/jira/browse/HDFS-14821
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 3.3.0
> Reporter: Stephen O'Donnell
> Assignee: Stephen O'Donnell
> Priority: Blocker
> Fix For: 3.3.0
>
> Attachments: HDFS-14821.001.patch
>
>
> In HDFS-14617 I incorrectly stated that a fsimage with sub-sections listed in
> the image summary section could be loaded without the HDFS-14617 patch
> applied. However that was not correct. If the cluster was upgraded to a
> version containing this feature, then upon downgrade the image will fail to
> load.
> I believe the simplest solution to this problem is to have this feature
> disabled by default. That way, after upgrading to a version with the feature,
> the operator can make a decision to enable the feature. If they later want to
> downgrade, then they must:
> # Disable the feature
> # Save the namespace, which will create an image without sub-sections
> # Perform the downgrade.
> Even though the steps to downgrade are simple, we cannot expect people to be
> aware of this, and hence it is safest to disable the feature by default.
> The only alternative is to create a new image layout version, but that seems
> excessive for this feature, as the core contents of the image have not
> changed and the sub-sections can be removed by disabling the feature and
> saving the namespace.
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