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https://issues.apache.org/jira/browse/HDFS-5889?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13899437#comment-13899437
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Jing Zhao commented on HDFS-5889:
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The new patch looks good to me. One question is that the current patch calls
"purgeOldStorage(NameNodeFile.IMAGE_ROLLBACK)" when finalizing rolling upgrade.
Looks like this method will still retain the IMAGE_ROLLBACK checkpoint (by
default, <= 2 ckpts)? Do we want to make sure the IMAGE_ROLLBACK checkpoint
gets purged here?
> When rolling upgrade is in progress, standby NN should create checkpoint for
> downgrade.
> ---------------------------------------------------------------------------------------
>
> Key: HDFS-5889
> URL: https://issues.apache.org/jira/browse/HDFS-5889
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: namenode
> Reporter: Tsz Wo (Nicholas), SZE
> Assignee: Tsz Wo (Nicholas), SZE
> Attachments: h5889_20140211.patch, h5889_20140212b.patch
>
>
> After rolling upgrade is started and checkpoint is disabled, the edit log may
> grow to a huge size. It is not a problem if rolling upgrade is finalized
> normally since NN keeps the current state in memory and it writes a new
> checkpoint during finalize. However, it is a problem if admin decides to
> downgrade. It could take a long time to apply edit log. Rollback does not
> have such problem.
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