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From "Josh Elser (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-118) accumulo could work across HDFS instances, which would help it to scale past a single namenode
Date Fri, 24 May 2013 00:38:20 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-118?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13665879#comment-13665879
] 

Josh Elser commented on ACCUMULO-118:
-------------------------------------

{quote}
With a different viewfs implementation, we could use a hash to
determine the namespace and hide the whole switch between file
systems:

hash("/accumulo/tables/1/default_tablet/A0003892.rf") % 2 -> hdfs://nn1:12345
hash("/accumulo/tables/1/default_tablet/F0004567.rf") % 2 -> hdfs://nn2:12345

Unfortunately, renaming a file might force it to a new namespace. 
{quote}

I bet you could be tricky with that actual hash+modulo in such a way which guarantees that
it wouldn't change namespaces.
                
> accumulo could work across HDFS instances, which would help it to scale past a single
namenode
> ----------------------------------------------------------------------------------------------
>
>                 Key: ACCUMULO-118
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-118
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: master, tserver
>            Reporter: Eric Newton
>            Assignee: Eric Newton
>            Priority: Blocker
>             Fix For: 1.6.0
>
>         Attachments: ACCUMULO-118-01.txt
>
>   Original Estimate: 2,016h
>  Remaining Estimate: 2,016h
>
> Consider using full path names to files, which would allow the servers to access the
files on any HDFS file system.
> Work may exist elsewhere to run HDFS using a number of NameNode instances to break up
the namespace.
> We may need a pluggable strategy to determine namespace for new files.

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