0.20: Allow block reports to proceed without holding FSDataset lock
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Key: HDFS-2379
URL: https://issues.apache.org/jira/browse/HDFS-2379
Project: Hadoop HDFS
Issue Type: Bug
Components: data-node
Affects Versions: 0.20.206.0
Reporter: Todd Lipcon
Priority: Critical
As disks are getting larger and more plentiful, we're seeing DNs with multiple
millions of blocks on a single machine. When page cache space is tight, block
reports can take multiple minutes to generate. Currently, during the scanning
of the data directories to generate a report, the FSVolumeSet lock is held.
This causes writes and reads to block, timeout, etc, causing big problems
especially for clients like HBase.
This JIRA is to explore some of the ideas originally discussed in HADOOP-4584
for the 0.20.20x series.
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