[ 
http://issues.apache.org/jira/browse/HADOOP-56?page=comments#action_12368011 ] 

Konstantin Shvachko commented on HADOOP-56:
-------------------------------------------

Format is definitely useful.
But I don't think it is reasonable to add GUID or any user information anywhere 
except
file description on the namenode. Otherwise it will be hard to support this 
information.
- The problem of different DFS installs writing to the same drive can be solved 
by introducing
DFS cluster name, and including it as a final component of dfs.name.dir and 
dfs.data.dir
- DFS probably needs an application version number, which should be compared 
when the
file system starts uploading information from the check pointed image.
And the conversion method, which if specified would provide conversion between 
the versions,
and if not the system should refuse loading the image. Sooner or later 
conversion of data will
become an issue, it would be good to have the mechanism in place by that time.


> hadoop nameserver does not recognise ndfs nameserver image
> ----------------------------------------------------------
>
>          Key: HADOOP-56
>          URL: http://issues.apache.org/jira/browse/HADOOP-56
>      Project: Hadoop
>         Type: Bug
>   Components: dfs
>     Versions: 0.1
>     Reporter: Yoram Arnon
>     Priority: Critical
>  Attachments: ndfs.tar.gz
>
> hadoop nameserver does not recognise ndfs image
> Thus, upgrading from ndfs to hadoop dfs results in total data loss.
> The upgrade should be seemless, with the new server recognising all previous 
> version that are not end-of-life'd.

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