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Posted to common-dev@hadoop.apache.org by "Amar Kamat (JIRA)" <ji...@apache.org> on 2008/03/28 12:32:26 UTC

[jira] Commented: (HADOOP-874) merge code is really slow

    [ https://issues.apache.org/jira/browse/HADOOP-874?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12582988#action_12582988 ] 

Amar Kamat commented on HADOOP-874:
-----------------------------------

Is this still valid? 

> merge code is really slow
> -------------------------
>
>                 Key: HADOOP-874
>                 URL: https://issues.apache.org/jira/browse/HADOOP-874
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: io
>    Affects Versions: 0.10.0
>            Reporter: Owen O'Malley
>            Assignee: Devaraj Das
>         Attachments: merge-no-seek.patch
>
>
> I had a case where the map output buffer size (io.sort.mb) was set too low and caused a spill and merge. Fixing the configuration caused it to not spill until it was finished. With the spill it took 9.5 minutes per a map. Without the spill it took 45 seconds. Therefore, I assume it was taking ~9 minutes to do the 2 file merge. That is really slow. The input files to the merge were two 25 mb sequence files (default codec (java), block compressed)

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