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From Ayon Sinha <ayonsi...@yahoo.com>
Subject Re: Question regarding datanode been wiped by hadoop
Date Tue, 12 Apr 2011 15:11:32 GMT
If you've only lost a few partitions on a data node and no loss of complete 
files due to replicated blocks, then I'd wipe the dfs.data.dir partitions and 
rebalance. It can get time-consuming to find the exact reason why the data 
blocks got removed. 
 -Ayon
See My Photos on Flickr
Also check out my Blog for answers to commonly asked questions.





________________________________
From: felix gao <gre1600@gmail.com>
To: hdfs-user@hadoop.apache.org
Sent: Tue, April 12, 2011 8:05:43 AM
Subject: Re: Question regarding datanode been wiped by hadoop

From the timestamp point of view, the only directory seems to be modified and 
removed is the Current directory under dfs.home.dir. However,  the storage file 
under dfs.home.dir is untouched since the datanode started.


On Tue, Apr 12, 2011 at 8:02 AM, felix gao <gre1600@gmail.com> wrote:

The xml files have not been changed for more than two months, so that should not 
be the reason.  Even the in_use.lock is more than a month old.  However, we did 
shut it down few days ago and restarted it afterward.  Then the second shutdown 
might not be clean. 
>
>
>
>On Tue, Apr 12, 2011 at 7:52 AM, Ayon Sinha <ayonsinha@yahoo.com> wrote:
>
>The datanode used the dfs config xml file to tell the datanode process, what 
>disks are available for storage. Can you check that the config xml has all the 
>partitions mentioned and has not been overwritten during the restore process?
>> -Ayon
>>See My Photos on Flickr
>>Also check out my Blog for answers to commonly asked questions.
>>
>>
>>
>>
>>
>>
________________________________
From: felix gao  <gre1600@gmail.com>
>>To: hdfs-user@hadoop.apache.org
>>Sent: Tue, April 12, 2011 7:46:31 AM
>>Subject: Question regarding datanode been wiped by hadoop
>>
>>
>>
>>What reason/condition would cause a datanode’s blocks to be removed?   Our 
>>cluster had a one of its datanodes crash because of bad RAM.   After the system 
>>was upgraded and the datanode/tasktracker brought online the next day we noticed 
>>the amount of space utilized was minimal and the cluster was rebalancing blocks 
>>to the datanode.   It would seem the prior blocks were removed.   Was this 
>>because the datanode was declared dead?   What is the criteria for a namenode to 
>>decide (Assuming its the namenode) when a datanode should remove prior blocks?  
>

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