[
https://issues.apache.org/jira/browse/HDFS-16613?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17634749#comment-17634749
]
Takanobu Asanuma commented on HDFS-16613:
-----------------------------------------
We found that this change and increasing
`dfs.namenode.replication.max-streams-hard-limit` have a side effect. Since it
affects not only ec files but also replication files, even if DataNodes have
only replication files, they will always generate high network traffic during
decommissioning even though the decommissioning speed is not much improved.
(Although decommissioning DataNodes with many replication files is already fast
enough.)
> 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
> Fix For: 3.4.0
>
> Attachments: image-2022-06-07-11-46-42-389.png,
> image-2022-06-07-17-42-16-075.png, image-2022-06-07-17-45-45-316.png,
> image-2022-06-07-17-51-04-876.png, image-2022-06-07-17-55-40-203.png,
> image-2022-06-08-11-38-29-664.png, image-2022-06-08-11-41-11-127.png
>
> Time Spent: 2.5h
> 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.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
---------------------------------------------------------------------
To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org
For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org
