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From "Konstantin Boudnik (JIRA)" <j...@apache.org>
Subject [jira] Reopened: (HDFS-503) Implement erasure coding as a layer on HDFS
Date Mon, 09 Nov 2009 17:59:32 GMT

     [ https://issues.apache.org/jira/browse/HDFS-503?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Konstantin Boudnik reopened HDFS-503:
-------------------------------------


Raid related tests are keep failing for a while now (http://hudson.zones.apache.org/hudson/view/Hadoop/job/Hadoop-Hdfs-trunk/135/console
and before):
{noformat}
    [junit] Tests run: 1, Failures: 0, Errors: 1, Time elapsed: 0.711 sec
    [junit] Test org.apache.hadoop.hdfs.TestRaidDfs FAILED
...
    [junit] Tests run: 2, Failures: 0, Errors: 2, Time elapsed: 0.632 sec
    [junit] Test org.apache.hadoop.raid.TestRaidNode FAILED
...
    [junit] Tests run: 1, Failures: 0, Errors: 1, Time elapsed: 0.461 sec
    [junit] Test org.apache.hadoop.raid.TestRaidPurge FAILED
{noformat}
It appears that some configuration options are incorrect.

> Implement erasure coding as a layer on HDFS
> -------------------------------------------
>
>                 Key: HDFS-503
>                 URL: https://issues.apache.org/jira/browse/HDFS-503
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: contrib/raid
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>             Fix For: 0.22.0
>
>         Attachments: raid1.txt, raid2.txt
>
>
> The goal of this JIRA is to discuss how the cost of raw storage for a HDFS file system
can be reduced. Keeping three copies of the same data is very costly, especially when the
size of storage is huge. One idea is to reduce the replication factor and do erasure coding
of a set of blocks so that the over probability of failure of a block remains the same as
before.
> Many forms of error-correcting codes are available, see http://en.wikipedia.org/wiki/Erasure_code.
Also, recent research from CMU has described DiskReduce https://opencirrus.org/system/files/Gibson-OpenCirrus-June9-09.ppt.
> My opinion is to discuss implementation strategies that are not part of base HDFS, but
is a layer on top of HDFS.

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