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https://issues.apache.org/jira/browse/HDFS-16613?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17545904#comment-17545904
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caozhiqiang commented on HDFS-16613:
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[~tasanuma] [~hadachi] , besides add a new configuration to limit
decommissioning dn separately, we also can use
dfs.namenode.replication.max-streams-hard-limit to impelements the same
purpose. We only need to modify DatanodeManager::handleHeartbeat() and use
dfs.namenode.replication.max-streams-hard-limit to give numReplicationTasks to
decommissioning dn. I will create a new pr, please help to review.
{code:java}
int maxTransfers;
if (nodeinfo.isDecommissionInProgress()) {
maxTransfers = blockManager.getReplicationStreamsHardLimit()
- xmitsInProgress;
} else {
maxTransfers = blockManager.getMaxReplicationStreams()
- xmitsInProgress;
} {code}
> EC: Improve performance of decommissioning dn with many ec blocks
> -----------------------------------------------------------------
>
> Key: HDFS-16613
> URL: https://issues.apache.org/jira/browse/HDFS-16613
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: ec, erasure-coding, namenode
> Affects Versions: 3.4.0
> Reporter: caozhiqiang
> Assignee: caozhiqiang
> Priority: Major
> Labels: pull-request-available
> Time Spent: 10m
> Remaining Estimate: 0h
>
> In a hdfs cluster with a lot of EC blocks, decommission a dn is very slow.
> The reason is unlike replication blocks can be replicated from any dn which
> has the same block replication, the ec block have to be replicated from the
> decommissioning dn.
> The configurations dfs.namenode.replication.max-streams and
> dfs.namenode.replication.max-streams-hard-limit will limit the replication
> speed, but increase these configurations will create risk to the whole
> cluster's network. So it should add a new configuration to limit the
> decommissioning dn, distinguished from the cluster wide max-streams limit.
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