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From "Travis Crawford (JIRA)" <j...@apache.org>
Subject [jira] Created: (HDFS-1312) Datanode storage directories fill unevenly
Date Wed, 21 Jul 2010 23:47:49 GMT
Datanode storage directories fill unevenly
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                 Key: HDFS-1312
                 URL: https://issues.apache.org/jira/browse/HDFS-1312
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: data-node
            Reporter: Travis Crawford


Filing this issue in response to ``full disk woes`` on hdfs-user.

Datanodes fill their storage directories unevenly, leading to situations where certain disks
are full while others are significantly less used. Users at many different sites have experienced
this issue, and HDFS administrators are taking steps like:

- Manually rebalancing blocks in storage directories
- Decomissioning nodes & later readding them


There's a tradeoff between making use of all available spindles, and filling disks at the
sameish rate. Possible solutions include:

- Weighting less-used disks heavier when placing new blocks on the datanode. In write-heavy
environments this will still make use of all spindles, equalizing disk use over time.
- Rebalancing blocks locally. This would help equalize disk use as disks are added/replaced
in older cluster nodes.


Datanodes should actively manage their local disk so operator intervention is not needed.

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