Jason Lowe created HDFS-6840:
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Summary: Clients are always sent to the same datanode when read is
off rack
Key: HDFS-6840
URL: https://issues.apache.org/jira/browse/HDFS-6840
Project: Hadoop HDFS
Issue Type: Bug
Affects Versions: 2.5.0
Reporter: Jason Lowe
Priority: Critical
After HDFS-6268 the sorting order of block locations is deterministic for a
given block and locality level (e.g.: local, rack. off-rack), so off-rack
clients all see the same datanode for the same block. This leads to very poor
behavior in distributed cache localization and other scenarios where many
clients all want the same block data at approximately the same time. The one
datanode is crushed by the load while the other replicas only handle local and
rack-local requests.
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