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Re: Shared Cluster between HBase and MapReduce
It depends... There are some reasons to do this however in general, you don't need to do this...

The course is wrong to suggest this as a best practice.

Sent from my iPhone

On Jun 5, 2012, at 5:00 PM, "Atif Khan" <[EMAIL PROTECTED]> wrote:

> During a recent Cloudera course we were told that it is "Best practice" to
> isolate a MapReduce/HDFS cluster from an HBase/HDFS cluster as the two when
> sharing the same HDFS cluster could lead to performance problems.  I am not
> sure if this is entirely true given the fact that the main concept behind
> Hadoop is to export computation to the data and not import data to the
> computation.  If I were to segregate HBase and MapReduce clusters, then when
> using MapReduce on HBase data would I not have to transfer large amounts of
> data from HBase/HDFS cluster to MapReduce/HDFS cluster?
> Cloudera on their best practice page
> (http://www.cloudera.com/blog/2011/04/hbase-dos-and-donts/) has the
> following:
> "Be careful when running mixed workloads on an HBase cluster. When you have
> SLAs on HBase access independent of any MapReduce jobs (for example, a
> transformation in Pig and serving data from HBase) run them on separate
> clusters. HBase is CPU and Memory intensive with sporadic large sequential
> I/O access while MapReduce jobs are primarily I/O bound with fixed memory
> and sporadic CPU. Combined these can lead to unpredictable latencies for
> HBase and CPU contention between the two. A shared cluster also requires
> fewer task slots per node to accommodate for HBase CPU requirements
> (generally half the slots on each node that you would allocate without
> HBase). Also keep an eye on memory swap. If HBase starts to swap there is a
> good chance it will miss a heartbeat and get dropped from the cluster. On a
> busy cluster this may overload another region, causing it to swap and a
> cascade of failures."
> All my initial investigation/reading lead me believe that I should a create
> a common HDFS cluster and then I can run MapReduce and HBase against the
> common HDFS cluster.   But from the above Cloudera best practice it seems
> like I should create two HDFS clusters, one for MapReduce and one for HBase
> and then move data around when required.  Something does not make sense with
> this best practice recommendation.
> Any thoughts and/or feedback will be much appreciated.
> --
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> Sent from the HBase User mailing list archive at Nabble.com.