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Subject: Re: Support of RHEL version
From: Alexander Alten-Lorenz <wget.null@gmail.com>
In-Reply-To: 
 <F0995027771CB14E9AE3C6BFB004D33313D6AF6B17@EXSFM-MB01.internal.salesforce.com>
Date: Thu, 24 Jan 2013 19:01:16 +0100
Cc: "cdh-user@cloudera.org" <cdh-user@cloudera.org>
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References: 
 <F361A6F9B4DBFD488940E5F58C0C839B133131B012@AUSX7MCPS302.AMER.DELL.COM>
 <DBCF22CB-5134-4ACD-88FA-0592B81461C6@gmail.com>
 <F0995027771CB14E9AE3C6BFB004D33313D6AF6B17@EXSFM-MB01.internal.salesforce.com>
To: "user@hadoop.apache.org user@hadoop.apache.org" <user@hadoop.apache.org>

Do you mean Transparent Huge Page Defrag =
(https://bugzilla.redhat.com/show_bug.cgi?id=3D805593)?

Do echo never > /sys/kernel/mm/redhat_transparent_hugepage/defrag

- Alex

On Jan 24, 2013, at 6:46 PM, Dheeren Bebortha <dbebortha@salesforce.com> =
wrote:

> I do not think this is a cdh specific issues. If this is a hbase =
compaction issue it would be all pervading as long as it si RHEL62 and =
above!
> Am I reading it right?
> -Dheeren
>=20
> -----Original Message-----
> From: Alexander Alten-Lorenz [mailto:wget.null@gmail.com]=20
> Sent: Thursday, January 24, 2013 9:41 AM
> To: cdh-user@cloudera.org
> Subject: Re: Support of RHEL version
>=20
> Hi,
>=20
> Moving the post to cdh-user@cloudera.org
> =
(https://groups.google.com/a/cloudera.org/forum/?fromgroups=3D#!forum/cdh-=
user)
> as it is CDH4 you specifically are asking about. BCC'd user@hadoop =
lists, lets carry forward the discussion on the CDH lists. My response =
below.
>=20
> RHEL 5.x and 6.x wil be supported. Means, RHEL 6.3 too.
>=20
> Cheers,
> Alex
>=20
> On Jan 24, 2013, at 6:28 PM, <Nilesh_Sangani@Dell.com> wrote:
>=20
>> Hi,
>>=20
>> 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?
>>=20
>> -Nilesh
>>=20
>>=20
>> =
https://ccp.cloudera.com/display/CDH4DOC/Known+Issues+and+Work+Arounds
>> +in+CDH4
>>=20
>>=20
>> Red Hat Linux (RHEL 6.2 and 6.3)
>> - Poor performance running Hadoop on RHEL 6.2 or later when=20
>> 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=3D805593
>> Severity: Medium (up to 3x performance loss) Anticipated Resolution:=20=

>> 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:
>> =
?<https://ccp.cloudera.com/display/CDH4DOC/Known+Issues+and+Work+Aroun
>> ds+in+CDH4> echo never >=20
>> /sys/kernel/mm/redhat_transparent_hugepage/defrag
>>=20
>>=20
>=20
> --
> Alexander Alten-Lorenz
> http://mapredit.blogspot.com
> German Hadoop LinkedIn Group: http://goo.gl/N8pCF
>=20

--
Alexander Alten-Lorenz
http://mapredit.blogspot.com
German Hadoop LinkedIn Group: http://goo.gl/N8pCF