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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2982) Startup performance suffers when there are many edit log segments
Date Mon, 21 May 2012 23:26:41 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2982?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13280613#comment-13280613
] 

Todd Lipcon commented on HDFS-2982:
-----------------------------------

Oops, missed part of my copy-paste comment:

{code}
+    LOG.info(this + ": selecting input streams starting at " + fromTxId +
+        (inProgressOk ? " (inProgress ok) " : " (excluding inProgress) ") +
+        "from among " + elfs.size() + " candidate file(s)");
{code}

This should probably be DEBUG level. Otherwise this will show up in the "safety check" selectInputStreams
call, and potentially confuse users.
                
> Startup performance suffers when there are many edit log segments
> -----------------------------------------------------------------
>
>                 Key: HDFS-2982
>                 URL: https://issues.apache.org/jira/browse/HDFS-2982
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: name-node
>    Affects Versions: 2.0.0
>            Reporter: Todd Lipcon
>            Assignee: Colin Patrick McCabe
>            Priority: Critical
>         Attachments: HDFS-2982.001.patch, HDFS-2982.002.patch, HDFS-2982.003.patch, HDFS-2982.004.patch,
HDFS-2982.005.patch, HDFS-2982.006.patch, HDFS-2982.007.patch, HDFS-2982.008.patch
>
>
> For every one of the edit log segments, it seems like we are calling listFiles on the
edit log directory inside of {{findMaxTransaction}}. This is killing performance, especially
when there are many log segments and the directory is stored on NFS. It is taking several
minutes to start up the NN when there are several thousand log segments present.

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