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https://issues.apache.org/jira/browse/HDFS-5526?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13826821#comment-13826821
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Kihwal Lee commented on HDFS-5526:
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What about adding the following in the beginning of
{{DataStorage.doRollback()}}? This is similar to what is in
{{DataStorage.doUpgrade()}}. Since the VERSION file is not read yet in rollback
(if it does it blows up as you reported), {{this.layoutVersion}} will be 0. So
instead, it is checking the software layout version and see whether it is using
the same layout version as the name node.
{code}
if (LayoutVersion.supports(Feature.FEDERATION, HdfsConstants.LAYOUT_VERSION)
&& HdfsConstants.LAYOUT_VERSION == nsInfo.getLayoutVersion()) {
clusterID = nsInfo.getClusterID();
layoutVersion = nsInfo.getLayoutVersion();
writeProperties(sd);
return;
}
{code}
> Datanode cannot roll back to previous layout version
> ----------------------------------------------------
>
> Key: HDFS-5526
> URL: https://issues.apache.org/jira/browse/HDFS-5526
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Reporter: Tsz Wo (Nicholas), SZE
> Priority: Blocker
>
> Current trunk layout version is -48.
> Hadoop v2.2.0 layout version is -47.
> If a cluster is upgraded from v2.2.0 (-47) to trunk (-48), the datanodes
> cannot start with -rollback. It will fail with IncorrectVersionException.
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