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From <Nilesh_Sang...@Dell.com>
Subject Support of RHEL version
Date Thu, 24 Jan 2013 17:28:59 GMT

We are working on implementing Cloudera distributed Hadoop (CDH 4.x) on our environment. 
Cloudera website talks about supporting RHEL 6.1 version with challenges/issues with the newer
version. It also though provides a workaround for it. Wanted to hear from the community on
the supported versions of RedHat Linux and any guidance on which version to choose?



Red Hat Linux (RHEL 6.2 and 6.3)
- Poor performance running Hadoop on RHEL 6.2 or later when transparent hugepage compaction
is enabled
RHEL 6.2 and 6.3 include a feature called "transparent hugepage compaction" which interacts
poorly with Hadoop workloads. This can cause a serious performance regression compared to
other operating system versions on the same hardware.
Symptom: top and other system monitoring tools show a large percentage of the CPU usage classified
as "system CPU". If system CPU usage is 30% or more of the total CPU usage, your system may
be experiencing this issue.
Bug: https://bugzilla.redhat.com/show_bug.cgi?id=805593
Severity: Medium (up to 3x performance loss)
Anticipated Resolution: Currently working with Red Hat to resolve for a future RHEL update
Workaround: Add the following command to /etc/rc.local to disable transparent hugepage compaction:
echo never > /sys/kernel/mm/redhat_transparent_hugepage/defrag

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