Block Replication should respect under-replication block priority
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Key: HDFS-1765
URL: https://issues.apache.org/jira/browse/HDFS-1765
Project: Hadoop HDFS
Issue Type: Improvement
Components: name-node
Affects Versions: 0.23.0
Reporter: Hairong Kuang
Assignee: Hairong Kuang
Fix For: 0.23.0
Currently under-replicated blocks are assigned different priorities depending
on how many replicas a block has. However the replication monitor works on
blocks in a round-robin fashion. So the newly added high priority blocks won't
get replicated until all low-priority blocks are done. One example is that on
decommissioning datanode WebUI we often observe that "blocks with only
decommissioning replicas" do not get scheduled to replicate before other
blocks, so risking data availability if the node is shutdown for repair before
decommission completes.
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