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From "Konstantin Shvachko (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-124) don't permit two datanodes to run from same dfs.data.dir
Date Thu, 18 May 2006 01:39:07 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-124?page=comments#action_12412273 ] 

Konstantin Shvachko commented on HADOOP-124:
--------------------------------------------

For future development in this direction.
We should persistently store on the name node all storage IDs, which the
name node ever assigned any blocks to.
With that knowledge the name node can reject blocks from any newly
registered data storages that are not on the name node list.
In other words when a data node registers NEW data storage it should not
report any blocks from that storage, and the name node can effectively verify 
that since it never assigned any blocks to this storage.
This would prevent us from accidentally connecting data nodes representing
different clusters (DFS instances).


> don't permit two datanodes to run from same dfs.data.dir
> --------------------------------------------------------
>
>          Key: HADOOP-124
>          URL: http://issues.apache.org/jira/browse/HADOOP-124
>      Project: Hadoop
>         Type: Bug

>   Components: dfs
>     Versions: 0.2
>  Environment: ~30 node cluster
>     Reporter: Bryan Pendleton
>     Assignee: Konstantin Shvachko
>     Priority: Critical
>      Fix For: 0.3
>  Attachments: DatanodeRegister.txt, DirNotSharing.patch
>
> 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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