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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Created: (HDFS-1295) Improve namenode restart times by short-circuiting the first block reports from datanodes
Date Mon, 12 Jul 2010 20:44:56 GMT
Improve namenode restart times by short-circuiting the first block reports from datanodes
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                 Key: HDFS-1295
                 URL: https://issues.apache.org/jira/browse/HDFS-1295
             Project: Hadoop HDFS
          Issue Type: Improvement
          Components: name-node
            Reporter: dhruba borthakur
            Assignee: dhruba borthakur
             Fix For: 0.22.0


The namenode restart is dominated by the performance of processing block reports. On a 2000
node cluster with 90 million blocks,  block report processing takes 30 to 40 minutes. The
namenode "diffs" the contents of the incoming block report with the contents of the blocks
map, and then applies these diffs to the blocksMap, but in reality there is no need to compute
the "diff" because this is the first block report from the datanode.

This code change improves block report processing time by 300%.

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