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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 Tue, 04 Feb 2014 03:24:11 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-118?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13890330#comment-13890330
] 

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

I think the short of it here: it's hard.

I remember when Eric was initially working on absolute paths and I thought "hrm, that's a
good idea. should simplify a lot of things in the end". In hindsight, I don't think I really
considered all of the difficulties that the changes introduce (most notably around upgrades
and namenode/namespace decommissioning).

Maintaining a long-running feature branch isn't too bad as long as the code you tweaked also
doesn't change out from underneath you.

I agree with you Keith, I think that focusing on design docs before starting to work on it
can help quite a bit on a couple of levels (avoid flaws in design, catch bugs earlier, net
a better architected solutions). Additionally, firming up a design can also help us break
down "really big" problems into "slightly less big" problems which will likely help manage
those changes. I think we've generally tried to abstain from requiring voting, but if that's
what we need to get eyes on ideas, so be it. If we can get good, thought-out reviews without
voting (which I think we've been fairly decent at so far, but we haven't had "big" designs
go through review yet), I'd rather stay that way.

> 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, ACCUMULO-118-02.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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