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From "Konstantin Shvachko (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-56) hadoop nameserver does not recognise ndfs nameserver image
Date Tue, 28 Feb 2006 19:19:42 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-56?page=comments#action_12368159 ] 

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

Sorry Bryan, I misinterpreted GUID as a group/user id.
So, yes a global unique id is for identifying particular data instances of the file system.
It can be generated by "format". And there shouldn't be any substantial overhead to support
this.

What I am trying to propose is to use the version number of the file system (as a software
application),
hard coded (rather than configured) and accessible via the getVersion() method, as a part
of GUID.
The version alone would have been sufficient to avoid the original problem
with data loss, but GUID provides even better consistency.
An additional advantage of versioning is that when the internal data layout for the name
or data nodes is changed, one can provide conversion methods from one version to another.


> 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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