[jira] Commented: (HADOOP-2576) Namenode performance degradation over time

> Namenode performance degradation over time
> ------------------------------------------
>
>                 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
>            Priority: Blocker
>             Fix For: 0.16.0
>
>
> 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.