farmmamba created HDFS-17484:
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             Summary: Introduce redundancy.considerLoad.minLoad to avoiding 
excluding nodes when they are not busy actually
                 Key: HDFS-17484
                 URL: https://issues.apache.org/jira/browse/HDFS-17484
             Project: Hadoop HDFS
          Issue Type: Improvement
          Components: namenode
    Affects Versions: 3.4.0
            Reporter: farmmamba
            Assignee: farmmamba


Currently, we have `dfs.namenode.redundancy.considerLoad` equals true by 
default, and 

dfs.namenode.redundancy.considerLoad.factor equals 2.0 by default.

Think about below situation. when we are doing stress test, we may deploy hdfs 
client onto the datanode. So, this hdfs client will prefer to write to its 
local datanode and increase this machine's load.  Suppose we have 3 datanodes, 
the load of them are as below:  5.0, 0.2, 0.3.

 

The load equals to 5.0 will be excluded when choose datanodes for a block. But 
actually, it is not slow node when load equals to 5.0 for a machine with 80 cpu 
cores.

 

So, we should better add a new configuration entry :  
`dfs.namenode.redundancy.considerLoad.minLoad` to indicate the mininum factor 
we will make considerLoad take effect.



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