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From "Owen O'Malley (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-124) Files still rotting in DFS of latest Hadoop
Date Fri, 07 Apr 2006 18:21:25 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-124?page=comments#action_12373675 ] 

Owen O'Malley commented on HADOOP-124:
--------------------------------------

It seems like it would help to have the datanode generate a unique identifier the first time
it is run, and save that in the data directory. On datanode restarts it uses the unique identifier
from the data directory. The namenode would be able to complain about multiple instance of
the same datanode.

> Files still rotting in DFS of latest Hadoop
> -------------------------------------------
>
>          Key: HADOOP-124
>          URL: http://issues.apache.org/jira/browse/HADOOP-124
>      Project: Hadoop
>         Type: Bug

>   Components: dfs
>  Environment: ~30 node cluster
>     Reporter: Bryan Pendleton

>
> DFS files are still rotting.
> I suspect that there's a problem with block accounting/detecting identical hosts in the
namenode. I have 30 physical nodes, with various numbers of local disks, meaning that my current
'bin/hadoop dfs -report" shows 80 nodes after a full restart. However, when I discovered the
 problem (which resulted in losing about 500gb worth of temporary data because of missing
blocks in some of the larger chunks) -report showed 96 nodes. I suspect somehow there were
extra datanodes running against the same paths, and that the namenode was counting those as
replicated instances, which then showed up over-replicated, and one of them was told to delete
its local block, leading to the block actually getting lost.
> I will debug it more the next time the situation arises. This is at least the 5th time
I've had a large amount of file data "rot" in DFS since January.

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