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From "Christopher Tubbs (JIRA)" <j...@apache.org>
Subject [jira] [Created] (ACCUMULO-3570) Relax restriction on instance.volumes.replacements so new volume does not have to be in instance.volumes
Date Fri, 06 Feb 2015 21:43:34 GMT
Christopher Tubbs created ACCUMULO-3570:
-------------------------------------------

             Summary: Relax restriction on instance.volumes.replacements so new volume does
not have to be in instance.volumes
                 Key: ACCUMULO-3570
                 URL: https://issues.apache.org/jira/browse/ACCUMULO-3570
             Project: Accumulo
          Issue Type: Bug
    Affects Versions: 1.6.1
            Reporter: Christopher Tubbs
            Assignee: Christopher Tubbs
             Fix For: 1.7.0, 1.6.3


ACCUMULO-1832 added the ability to replace volume references with a differently named volume.

However, it also added a restriction that the new volume must be specified in the {{instance.volumes}}
set. While that is a use case, it is an unnecessary restriction and conflates the purpose
of replacements with regular volumes. {{instance.volumes}} is the set of volumes to write
new tablets files to, while the replacements are intended to assign in remapping references
to already written data, so it can be read.

One use case that this restriction prevents, for example, is migrating from failing hardware
to a new cluster. A user may rename the old namenode from "nn" to "nn-old", and name the new
one "nn-new", but wouldn't want new files to be written to "nn-old". This could be achieved
by a custom volume chooser which blacklists "nn-old" for new tablets, but that would require
writing custom code. Relaxing this restriction allows users to get the same behavior in configuration.



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