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From "Todd Lipcon (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2379) 0.20: Allow block reports to proceed without holding FSDataset lock
Date Mon, 03 Oct 2011 17:13:34 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2379?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13119409#comment-13119409
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Todd Lipcon commented on HDFS-2379:
-----------------------------------

I've been testing this latest patch for several days now, with terasorts, teragens, etc, and
no issues to be seen. I tested both with a small number of blocks per node, and with a large
number per node (by adding a few TB with 256KB block size)
                
> 0.20: Allow block reports to proceed without holding FSDataset lock
> -------------------------------------------------------------------
>
>                 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
>         Attachments: hdfs-2379.txt, hdfs-2379.txt
>
>
> 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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