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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-2576) Namenode performance degradation over time
Date Fri, 25 Jan 2008 01:06:34 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-2576?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12562323#action_12562323
] 

dhruba borthakur commented on HADOOP-2576:
------------------------------------------

FSNamesystem.blockInvalidateLimit shoudl be initialized to  FSConstants.BLOCK_INVALIDATE_CHUNK.

The heartbeatInterval is in milliseconds. Do you really want the blockInvalidateLimit to be
set to 20 times the number of milliseconds in a heartbeat interval? That seems to high.



> Namenode performance degradation over time
> ------------------------------------------
>
>                 Key: HADOOP-2576
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2576
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.16.0
>            Reporter: Christian Kunz
>            Assignee: Raghu Angadi
>            Priority: Blocker
>             Fix For: 0.16.0
>
>         Attachments: HADOOP-2576.patch, HADOOP-2576.patch
>
>
> 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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