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From "Matt Foley (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-1295) Improve namenode restart times by short-circuiting the first block reports from datanodes
Date Sun, 17 Apr 2011 20:48:06 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1295?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13020865#comment-13020865
] 

Matt Foley commented on HDFS-1295:
----------------------------------

The unit test files cited in HDFS-1806, HDFS-1808, HDFS-1827, HDFS-1828, and HDFS-1829, were
all found to be failing for reasons unrelated to the patch for this bug, HDFS-1295.  I'm submitting
fixes for each of them, but I've detached them from this bug.  Please review them separately.
 Thanks.

> Improve namenode restart times by short-circuiting the first block reports from datanodes
> -----------------------------------------------------------------------------------------
>
>                 Key: HDFS-1295
>                 URL: https://issues.apache.org/jira/browse/HDFS-1295
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>    Affects Versions: 0.22.0
>            Reporter: dhruba borthakur
>            Assignee: Matt Foley
>             Fix For: 0.23.0
>
>         Attachments: IBR_shortcut_v2a.patch, IBR_shortcut_v3atrunk.patch, IBR_shortcut_v4atrunk.patch,
IBR_shortcut_v4atrunk.patch, IBR_shortcut_v4atrunk.patch, shortCircuitBlockReport_1.txt
>
>
> 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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