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Wei-Chiu Chuang commented on HDFS-14821: ---------------------------------------- +1 best to avoid the complication of rolling upgrades/downgrades. We've seen how it played out with EC (HDFS-13596/HDFS-14396) > 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 > > 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. -- This message was sent by Atlassian Jira (v8.3.2#803003) --------------------------------------------------------------------- To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org