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Posted to hdfs-issues@hadoop.apache.org by "tomscut (Jira)" <ji...@apache.org> on 2021/06/29 11:47:00 UTC
[jira] [Comment Edited] (HDFS-16093) DataNodes under decommission
will still be returned to the client via getLocatedBlocks, so the client
may request decommissioning datanodes to read which will cause badly
competation on disk IO.
[ https://issues.apache.org/jira/browse/HDFS-16093?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17371306#comment-17371306 ]
tomscut edited comment on HDFS-16093 at 6/29/21, 11:46 AM:
-----------------------------------------------------------
IMO, abnormal nodes cannot be removed directly. Maybe sorting is a better choice, because it makes it easier to degrade read when there are not enough normal nodes. Just like the example [~sodonnell] gave.
See org.apache.hadoop.hdfs.DFSInputStream#getBestNodeDNAddrPair().
was (Author: tomscut):
IMO, abnormal nodes cannot be removed directly. Maybe sorting is a better choice, because it makes it easier to degrade read when there are not enough normal nodes. Just like the example [~sodonnell] gave.
> DataNodes under decommission will still be returned to the client via getLocatedBlocks, so the client may request decommissioning datanodes to read which will cause badly competation on disk IO.
> --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: HDFS-16093
> URL: https://issues.apache.org/jira/browse/HDFS-16093
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 3.3.1
> Reporter: Daniel Ma
> Priority: Critical
>
> DataNodes under decommission will still be returned to the client via getLocatedBlocks, so the client may request decommissioning datanodes to read which will cause badly competation on disk IO.
> Therefore, datanodes under decommission should be removed from the return list of getLocatedBlocks api.
> !image-2021-06-29-10-50-44-739.png!
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