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Re: how to handle the corrupt block in HDFS?
thanks for reply, what i do not know is how can i locate the block which
has the corrupt replica,(so i can observe how long the corrupt replica will
be removed and a new health replica replace it,because i get nagios alert
for three days,i do not sure if it is the same corrupt replica cause the
alert ,and i do not know the interval of hdfs check corrupt replica and
clean it)

On Tue, Dec 10, 2013 at 6:20 PM, Vinayakumar B <[EMAIL PROTECTED]>wrote:

>  Hi ch huang,
>
>
>
> It may seem strange, but the fact is,
>
> *CorruptBlocks* through JMX means *“Number of blocks with corrupt
> replicas”. May not be all replicas are corrupt.  *This you can check
> though jconsole for description.
>
>
>
> Where as *Corrupt blocks* through fsck means, *blocks with all replicas
> corrupt(non-recoverable)/ missing.*
>
>
>
> In your case, may be one of the replica is corrupt, not all replicas of
> same block. This corrupt replica will be deleted automatically if one more
> datanode available in your cluster and block replicated to that.
>
>
>
>
>
> Related to replication 10, As Peter Marron said, *some of the important
> files of the mapreduce job will set the replication of 10, to make it
> accessible faster and launch map tasks faster. *
>
> Anyway, if the job is success these files will be deleted auomatically. I
> think only in some cases if the jobs are killed in between these files will
> remain in hdfs showing underreplicated blocks.
>
>
>
> Thanks and Regards,
>
> Vinayakumar B
>
>
>
> *From:* Peter Marron [mailto:[EMAIL PROTECTED]]
> *Sent:* 10 December 2013 14:19
> *To:* [EMAIL PROTECTED]
> *Subject:* RE: how to handle the corrupt block in HDFS?
>
>
>
> Hi,
>
>
>
> I am sure that there are others who will answer this better, but anyway.
>
> The default replication level for files in HDFS is 3 and so most files
> that you
>
> see will have a replication level of 3. However when you run a Map/Reduce
>
> job the system knows in advance that every node will need a copy of
>
> certain files. Specifically the job.xml and the various jars containing
>
> classes that will be needed to run the mappers and reducers. So the
>
> system arranges that some of these files have a higher replication level.
> This increases
>
> the chances that a copy will be found locally.
>
> By default this higher replication level is 10.
>
>
>
> This can seem a little odd on a cluster where you only have, say, 3 nodes.
>
> Because it means that you will almost always have some blocks that are
> marked
>
> under-replicated. I think that there was some discussion a while back to
> change
>
> this to make the replication level something like min(10, #number of nodes)
>
> However, as I recall, the general consensus was that this was extra
>
> complexity that wasn’t really worth it. If it ain’t broke…
>
>
>
> Hope that this helps.
>
>
>
> *Peter Marron*
>
> Senior Developer, Research & Development
>
>
>
> Office: +44 *(0) 118-940-7609*  [EMAIL PROTECTED]
>
> Theale Court First Floor, 11-13 High Street, Theale, RG7 5AH, UK
>
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>
>  <https://twitter.com/TrilliumSW>
>
>  <http://www.linkedin.com/company/17710>
>
>
>
> *www.trilliumsoftware.com <http://www.trilliumsoftware.com/>*
>
> Be Certain About Your Data. Be Trillium Certain.
>
>
>
> *From:* ch huang [mailto:[EMAIL PROTECTED] <[EMAIL PROTECTED]>]
> *Sent:* 10 December 2013 01:21
> *To:* [EMAIL PROTECTED]
> *Subject:* Re: how to handle the corrupt block in HDFS?
>
>
>
> more strange , in my HDFS cluster ,every block has three replicas,but i
> find some one has ten replicas ,why?
>
>
>
> # sudo -u hdfs hadoop fs -ls
> /data/hisstage/helen/.staging/job_1385542328307_0915
> Found 5 items
> -rw-r--r--   3 helen hadoop          7 2013-11-29 14:01
> /data/hisstage/helen/.staging/job_1385542328307_0915/appTokens
> -rw-r--r--  10 helen hadoop    2977839 2013-11-29 14:01
> /data/hisstage/helen/.staging/job_1385542328307_0915/job.jar