Liu Shaohui created HDFS-8131:
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Summary: Implement a space blance block placement policy
Key: HDFS-8131
URL: https://issues.apache.org/jira/browse/HDFS-8131
Project: Hadoop HDFS
Issue Type: Improvement
Reporter: Liu Shaohui
Assignee: Liu Shaohui
Priority: Minor
The default block placement policy will choose datanodes for new blocks
randomly, which will result in unbalanced space used percent among datanodes
after an cluster expansion. The old datanodes always are in high used percent
of space and new added ones are in low percent.
Through we can used the external balance tool to balance the space used rate,
it will cost extra network IO and it's not easy to control the balance speed.
An easy solution is to implement an balanced block placement policy which will
choose low used percent datanodes for new blocks with a little high
possibility. In a not long term, the used percent of datanodes will trend to be
balanced.
Suggestions and discussions are welcomed. Thanks
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