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From "Christopher Tubbs (JIRA)" <>
Subject [jira] [Created] (ACCUMULO-3090) VolumeChooser should be able to decide per-file
Date Thu, 28 Aug 2014 23:19:08 GMT
Christopher Tubbs created ACCUMULO-3090:

             Summary: VolumeChooser should be able to decide per-file
                 Key: ACCUMULO-3090
             Project: Accumulo
          Issue Type: Improvement
    Affects Versions: 1.6.0
            Reporter: Christopher Tubbs

Currently, the VolumeChooser decides only once per-tablet which volume to use for that tablet.
The directory is "sticky" after the decision is made. This can cause unexpected behavior for
users, which makes it harder to manage volume usage/capacity.

One unexpected behavior is that data will still be written to an existing tablet's predetermined
volume, even if the volume is removed from instance.volumes.

Another unexpected behavior this causes for users is when adding a new volume. One might expect
to compact tablets after adding a new volume, and have the new usage to be balanced across
all the volumes (using the provided RandomVolumeChooser), but due to the stickiness, that
is not the behavior seen. Instead, only new tablets (from new tables, or new splits) will
begin to randomly use the new volume.

If the sticky behavior is desired, a volume chooser could still do that, by accepting a "preferredTabletVolume"/"preferredTabletDirectory"
in its environment, provided by the caller, to use to make decisions.

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