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HBase >> mail # dev >> Max xceiver config


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Laxman 2012-03-22, 05:43
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Re: Max xceiver config
Hi Laxman,

Did you see (sorry for the plug) http://www.larsgeorge.com/2012/03/hadoop-hbase-and-xceivers.html - it might help determining the number.

Lars

On Mar 22, 2012, at 6:43 AM, Laxman wrote:

> HBase book is recommending to set xceiver count[dfs.datanode.max.xcievers]
> to 4096
> http://hbase.apache.org/book.html#hadoop
>
> Why do we need to have xceivers count so high as 4096?
>
> This means each Datanode in cluster is allowing the maximum of
>  - 4096 threads with each thread occupying some memory
>  - 4096 threads read/write to the disk(s) simultaneously
>
> This actually makes the system more vulnerable (kind of DOS attacks) by
> over-utilization of the system resources.
>
> Also, this recommendation was based on some issue reported on Hadoop 0.18.
> IMO, we should not have such high value as recommendation/default value and
> this value to be tuned as per the capacity requirements.
>
> Related issues
> =============> HDFS-162
>  - Reported on 0.18
>  - Raising xciever count to high value caused other problems.
>  - Resolution "Cannot Reproduce "
>
> HDFS-1861
>  - Modified the default value to 4096
>  - Source
> http://ccgtech.blogspot.in/2010/02/hadoop-hdfs-deceived-by-xciever.html
> which again refers to HDFS-162 (Reported on 0.18).
>
> Case study
> =========> http://lucene.472066.n3.nabble.com/Blocks-are-getting-corrupted-under-very-h
> igh-load-tc3527403.html
> In one of our production environment, this value has been set to 4096 and
> disk waits were very huge due to which some processes were not responding.
> Also OS is configured to reboot (kernel panic reboot) when some process is
> not responding for a specific amount of time.
>
> These two configurations has resulted in corrupted data.
> --
> Regards,
> Laxman
>
>
>
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Ramkrishna.S.Vasudevan 2012-03-22, 13:31
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Doug Meil 2012-03-22, 14:10
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Laxman 2012-03-22, 12:51
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lars hofhansl 2012-03-22, 16:43