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https://issues.apache.org/jira/browse/HBASE-21806?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16782228#comment-16782228
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Sergey Shelukhin commented on HBASE-21806:
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It could be added as another jira. In our case we have many DNs so it's
unlikely. For small clusters it could be more likely, OTOH if the cluster is
really small it can cause problems with load skew on datanodes or even not
having enough to replicate after exclusions.
> add an option to roll WAL on very slow syncs
> --------------------------------------------
>
> Key: HBASE-21806
> URL: https://issues.apache.org/jira/browse/HBASE-21806
> Project: HBase
> Issue Type: Improvement
> Reporter: Sergey Shelukhin
> Assignee: Sergey Shelukhin
> Priority: Major
> Fix For: 3.0.0
>
> Attachments: HBASE-21806.patch
>
>
> In large heterogeneous clusters sometimes a slow datanode can cause WAL syncs
> to be very slow. In this case, before the bad datanode recovers, or is
> discovered and repaired, it would be helpful to roll WAL on a very slow sync
> to get a new pipeline.
> Otherwise the slow WAL will impact write latency for a long time (slow writes
> result in less writes result in the WAL not being rolled for longer)
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