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From "Christian Kunz (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-2576) Namenode performance degradation over time
Date Fri, 11 Jan 2008 06:01:38 GMT
Namenode performance degradation over time
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                 Key: HADOOP-2576
                 URL: https://issues.apache.org/jira/browse/HADOOP-2576
             Project: Hadoop
          Issue Type: Bug
          Components: dfs
    Affects Versions: 0.16.0
            Reporter: Christian Kunz


We have a cluster running the same applications again and again with a high turnover of files.

The performance of these applications seem to be correlated to the lifetime of the namenode:
After starting the namenode, the applications need increasingly more time to complete, with
about 50% more time after 1 week. 

During that time the namenode average cpu usage increases from typically 10% to 30%, memory
usage nearly doubles (although the average amount of data on dfs stays the same), and the
average load factor increases by a factor of 2-3 (although not  significantly high, <2).

When looking at the namenode and datanode logs, I see a lot of asks to delete blocks coming
from the namenode for blocks not in the blockmap of the datanodes, repeatedly for the same
blocks.
When I counted the number of blocks asked by the namenode to be deleted, I noticed a noticeable
increase with the lifetime of the namenode (a factor of 2-3 after 1 week).

This makes me wonder whether the namenode does not purge the list of invalid blocks from non-existing
blocks.

But independently, the namenode has a degradation issue.

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