All replicas of a block end up on only 1 rack
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Key: HADOOP-4477
URL: https://issues.apache.org/jira/browse/HADOOP-4477
Project: Hadoop Core
Issue Type: Bug
Components: dfs
Reporter: Hairong Kuang
Assignee: Hairong Kuang
Priority: Critical
Fix For: 0.20.0
HDFS replicas placement strategy guarantees that the replicas of a block exist
on at least two racks when its replication factor is greater than one. But fsck
still reports that the replicas of some blocks end up on one rack.
The cause of the problem is that decommission and corruption handling only
check the block's replication factor but not the rack requirement. When an
over-replicated block loses a replica due to decomission, corruption, or
heartbeat lost, namenode does not take any action to guarantee that remaining
replicas are on different racks.
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