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From "Josh Elser (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-3540) Allow settting instance_volumes and instance_volumes_replacements via zk
Date Tue, 27 Jan 2015 23:59:34 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-3540?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14294443#comment-14294443
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Josh Elser commented on ACCUMULO-3540:
--------------------------------------

I think this makes sense. Back when we only had a single DFS directory for Accumulo, mutability
made no sense. Since we can grow/shrink volumes, I think it's acceptable to let these be changed
on the fly.

If we let them be mutable, it's also worth thinking about whether or not they still need to
be consistent across an instance. I'm not entirely decided if we want to allow variance of
the values across a single instance (moving the property out of the {{instance.}} prefix so
it wouldn't break the SystemToken). I could think of a case where there are multiple HDFS
instances that make up a very large Accumulo instance. Each HDFS instance is connected, but
has faster network connections "locally" (e.g. networks 10.1.0.0/16, 10.2.0.0/16, and 10.3.0.0/16
each run an HDFS instance). Tablet servers in each class B network would want to use the HDFS
instance running on that network. There would be some work in assignment/recovery to actually
make that work, but I think it is a plausible situation. However, I'm not sure if it's worth
the hassle to try to support right now.

> Allow settting instance_volumes and instance_volumes_replacements via zk
> ------------------------------------------------------------------------
>
>                 Key: ACCUMULO-3540
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-3540
>             Project: Accumulo
>          Issue Type: Bug
>            Reporter: John Vines
>
> Currently these settings are under the catch-all of no instance keys allowed in zk. Unfortunately,
I feel that's a bit far reaching as these two settings, I feel, don't need to be accumulo-site.xml
only. These spaces shouldn't be used until after we get ZK information. Furthermore, now that
we support multiple filesystems, our current implementation does not allow us to dynamically
add more filesystems, so that would be another benefit.



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