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HDFS, mail # user - Unbalanced disks - need to take down whole HDFS?


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Re: Unbalanced disks - need to take down whole HDFS?
Travis Crawford 2010-12-16, 14:44
On Dec 16, 2010, at 6:34 AM, Erik Forsberg <[EMAIL PROTECTED]> wrote:

> Hi!
>
> I have unbalanced disks on one of my nodes after a disk failure with
> disk replacements.
>
> http://wiki.apache.org/hadoop/FAQ#On_an_individual_data_node.2C_how_do_you_balance_the_blocks_on_the_disk.3F
> has a solution, but it starts with "Take down HDFS".
>
> Is that really necessary - shouldn't taking down just that datanode,
> moving around the blocks, then start the datanode be good enough, or
> will that mess up some datastructure in the namenode?
>

You're right - that should say take the DataNode down, move blocks
around, then restart the DataNode. You might be able to just replace
the disk and have them unbalanced for a while though. As data is
created and deleted things will naturally even out.

--Travis

> Thanks,
> \EF
> --
> Erik Forsberg <[EMAIL PROTECTED]>
> Developer, Opera Software - http://www.opera.com/