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HDFS, mail # user - disk used percentage is not symmetric on datanodes (balancer)


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Re: disk used percentage is not symmetric on datanodes (balancer)
Tapas Sarangi 2013-03-19, 01:25

On Mar 18, 2013, at 6:17 PM, Bertrand Dechoux <[EMAIL PROTECTED]> wrote:

> And by active, it means that it does actually stops by itself?
> Else it might mean that the throttling/limit might be an issue with regard to the data volume or velocity.
>

This "else" is probably what's happening. I just checked the logs. Its active almost all the time.
> What threshold is used?

Don't know what's this. How can I find out ?

>
> About the small and big datanodes, how are they distributed with regards to racks?

We haven't considered rack awareness for our cluster. It is currently considered as one rack. I am going through some docs to figure out how I can implement this after the upgrade.

> About files, how is used the replication factor(s) and block size(s)?

This is 2.

>
> Surely trivial questions again.
>

Not really :)

Thanks
-Tapas
> Bertrand
>
> On Mon, Mar 18, 2013 at 10:46 PM, Tapas Sarangi <[EMAIL PROTECTED]> wrote:
> Hi,
>
> Sorry about that, had it written, but thought it was obvious.
> Yes, balancer is active and running on the namenode.
>
> -Tapas
>
> On Mar 18, 2013, at 4:43 PM, Bertrand Dechoux <[EMAIL PROTECTED]> wrote:
>
>> Hi,
>>
>> It is not explicitly said but did you use the balancer?
>> http://hadoop.apache.org/docs/r1.0.4/commands_manual.html#balancer
>>
>> Regards
>>
>> Bertrand
>>
>> On Mon, Mar 18, 2013 at 10:01 PM, Tapas Sarangi <[EMAIL PROTECTED]> wrote:
>> Hello,
>>
>> I am using one of the old legacy version (0.20) of hadoop for our cluster. We have scheduled for an upgrade to the newer version within a couple of months, but I would like to understand a couple of things before moving towards the upgrade plan.
>>
>> We have about 200 datanodes and some of them have larger storage than others. The storage for the datanodes varies between 12 TB to 72 TB.
>>
>> We found that the disk-used percentage is not symmetric through all the datanodes. For larger storage nodes the percentage of disk-space used is much lower than that of other nodes with smaller storage space. In larger storage nodes the percentage of used disk space varies, but on average about 30-50%. For the smaller storage nodes this number is as high as 99.9%. Is this expected ? If so, then we are not using a lot of the disk space effectively. Is this solved in a future release ?
>>
>> If no, I would like to know  if there are any checks/debugs that one can do to find an improvement with the current version or upgrading hadoop should solve this problem.
>>
>> I am happy to provide additional information if needed.
>>
>> Thanks for any help.
>>
>> -Tapas
>>
>
>
>
>
> --
> Bertrand Dechoux