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Date: Sat, 14 May 2011 03:25:47 +0000 (UTC)
From: "Bharath Mundlapudi (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Assigned] (HDFS-1940) Datanode can have more than one copy
 of same block when a failed disk is coming back in datanode
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     [ https://issues.apache.org/jira/browse/HDFS-1940?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Bharath Mundlapudi reassigned HDFS-1940:
----------------------------------------

    Assignee: Bharath Mundlapudi

> Datanode can have more than one copy of same block when a failed disk is coming back in datanode
> ------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-1940
>                 URL: https://issues.apache.org/jira/browse/HDFS-1940
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: data-node
>    Affects Versions: 0.20.204.0
>            Reporter: Rajit
>            Assignee: Bharath Mundlapudi
>
> There is a situation where one datanode can have more than one copy of same block due to a disk fails and comes back after sometime in a datanode. And these duplicate blocks are not getting deleted even after datanode and namenode restart.
> This situation can only happen in a corner case , when due to disk failure, the data block is replicated to other disk of the same datanode.
> To simulate this scenario I copied a datablock and the associated .meta file from one disk to another disk of same datanode, so the datanode is having 2 copy of same replica. Now I restarted datanode and namenode. Still the extra data block and meta file is not deleted from the datanode
> [hdfs@gsbl90192 rajsaha]$ ls -l `find /grid/{0,1,2,3}/hadoop/var/hdfs/data/current -name blk_*`
> -rw-r--r-- 1 hdfs users 7814 May 13 21:05 /grid/1/hadoop/var/hdfs/data/current/blk_1727421609840461376
> -rw-r--r-- 1 hdfs users   71 May 13 21:05 /grid/1/hadoop/var/hdfs/data/current/blk_1727421609840461376_579992.meta
> -rw-r--r-- 1 hdfs users 7814 May 13 21:14 /grid/3/hadoop/var/hdfs/data/current/blk_1727421609840461376
> -rw-r--r-- 1 hdfs users   71 May 13 21:14 /grid/3/hadoop/var/hdfs/data/current/blk_1727421609840461376_579992.meta

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