CentOS 5.4 x86_64 only detects 32GB RAM while Fedora x86_64 correctly lists 128GB

12-07-2009, 11:05 AM

Hi,
We have a new 24-core Dell PowerEdge R905 server with 128GB's RAM. The 64 bits version of Fedora 12 lists the correct amount of 128GB, CentOS only finds 32GB (and so does Scientific Linux). I would much prefer to use CentOS (most of the software we use is specifically designed for CentOS). Does anyone know what is causing this/how to fix it?
Many Thanks,
Diederick_________________________________________ ______
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12-07-2009, 11:12 AM

what kernel are you running?

On Mon, Dec 7, 2009 at 2:05 PM, Diederick Stoffers <d.stoffers@gmail.com> wrote:
> Hi,
> We have a new 24-core Dell PowerEdge R905 server with 128GB's RAM. The 64
> bits version of Fedora 12 lists the correct amount of 128GB, CentOS only
> finds 32GB (and so does Scientific Linux). I would much prefer to use CentOS
> (most of the software we use is specifically designed for CentOS). Does
> anyone know what is causing this/how to fix it?
> Many Thanks,
> Diederick
> _______________________________________________
> CentOS mailing list
> CentOS@centos.org
> http://lists.centos.org/mailman/listinfo/centos
>
>

--
Kind Regards
Rudi Ahlers
CEO, SoftDux Hosting
Web: http://www.SoftDux.com
Office: 087 805 9573
Cell: 082 554 7532
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12-07-2009, 11:24 AM

[root@localhost ~]# uname -aLinux localhost.localdomain 2.6.18-164.6.1.el5xen #1 SMP Tue Nov 3 16:48:13 EST 2009 x86_64 x86_64 x86_64 GNU/Linux

On 7 dec 2009, at 13:12, Rudi Ahlers wrote:what kernel are you running?

On Mon, Dec 7, 2009 at 2:05 PM, Diederick Stoffers <d.stoffers@gmail.com> wrote:
Hi,
We have a new 24-core Dell PowerEdge R905 server with 128GB's RAM. The 64
bits version of Fedora 12 lists the correct amount of 128GB, CentOS only
finds 32GB (and so does Scientific Linux). I would much prefer to use CentOS
(most of the software we use is specifically designed for CentOS). Does
anyone know what is causing this/how to fix it?
Many Thanks,
Diederick
_______________________________________________
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http://lists.centos.org/mailman/listinfo/centos

--
Kind Regards
Rudi Ahlers
CEO, SoftDux Hosting
Web: http://www.SoftDux.com
Office: 087 805 9573
Cell: 082 554 7532
_______________________________________________
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12-07-2009, 12:42 PM

Thanks! Virtualisation limits RAM to 32GB, removing this from the package does the trick.
Cheers,
Diederick
On 7 dec 2009, at 13:35, Nickolay Bunev wrote:Hi,
It seems that this links shed light on the question:
http://lists.xensource.com/archives/html/xen-users/2008-08/msg00934.html
http://www.centos.org/docs/5/html/5.1/Virtualization_Guide/ch-virt-hw-support.html

On 12/07/2009 02:05 PM, Diederick Stoffers wrote:
Hi,

We have a new 24-core Dell PowerEdge R905 server with 128GB's RAM. The
64 bits version of Fedora 12 lists the correct amount of 128GB, CentOS
only finds 32GB (and so does Scientific Linux). I would much prefer to
use CentOS (most of the software we use is specifically designed for
CentOS). Does anyone know what is causing this/how to fix it?

Many Thanks,

Diederick

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12-07-2009, 12:49 PM

On Monday 07 December 2009, Diederick Stoffers wrote:
> Hi,
>
> We have a new 24-core Dell PowerEdge R905 server with 128GB's RAM. The 64
> bits version of Fedora 12 lists the correct amount of 128GB, CentOS only
> finds 32GB (and so does Scientific Linux).

Hmm.. maybe this has to do with the Xen kernel. Redhat says x86_64 should do
256G/1T (AMD/Intel) and we're successfully running 72G on Centos-5.4.

/Peter

> I would much prefer to use
> CentOS (most of the software we use is specifically designed for CentOS).
> Does anyone know what is causing this/how to fix it?
>
> Many Thanks,
>
> Diederick
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12-07-2009, 08:35 PM

On Mon, Dec 7, 2009 at 12:24 PM, Diederick Stoffers
<d.stoffers@gmail.com> wrote:
> [root@localhost ~]# uname -a
> Linux localhost.localdomain 2.6.18-164.6.1.el5xen #1 SMP Tue Nov 3 16:48:13
> EST 2009 x86_64 x86_64 x86_64 GNU/Linux
>
> On 7 dec 2009, at 13:12, Rudi Ahlers wrote:
>
> what kernel are you running?
>
> On Mon, Dec 7, 2009 at 2:05 PM, Diederick Stoffers <d.stoffers@gmail.com>
> wrote:
>
> Hi,
>
> We have a new 24-core Dell PowerEdge R905 server with 128GB's RAM. The 64
>
> bits version of Fedora 12 lists the correct amount of 128GB, CentOS only
>
> finds 32GB (and so does Scientific Linux). I would much prefer to use CentOS
>
> (most of the software we use is specifically designed for CentOS). Does
>
> anyone know what is causing this/how to fix it?
>
> Many Thanks,
>
> Diederick
>
> _______________________________________________
>
> CentOS mailing list
>
> CentOS@centos.org
>
> http://lists.centos.org/mailman/listinfo/centos
>
>
>
>
>
> --
> Kind Regards
> Rudi Ahlers
> CEO, SoftDux Hosting
> Web: http://www.SoftDux.com
> Office: 087 805 9573
> Cell: 082 554 7532
> _______________________________________________
> CentOS mailing list
> CentOS@centos.org
> http://lists.centos.org/mailman/listinfo/centos
>
>
> _______________________________________________
> CentOS mailing list
> CentOS@centos.org
> http://lists.centos.org/mailman/listinfo/centos
>
>

Try to run xentop (xm top) and see if it displays the correct ammount of memory.
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12-07-2009, 08:49 PM

On Mon, Dec 7, 2009 at 4:35 PM, Lucian @ lastdot.org <lucian@lastdot.org> wrote:

On Mon, Dec 7, 2009 at 12:24 PM, Diederick Stoffers

<d.stoffers@gmail.com> wrote:

> [root@localhost ~]# uname -a

> Linux localhost.localdomain 2.6.18-164.6.1.el5xen #1 SMP Tue Nov 3 16:48:13

> EST 2009 x86_64 x86_64 x86_64 GNU/Linux

>

> On 7 dec 2009, at 13:12, Rudi Ahlers wrote:

>

> what kernel are you running?

>

> On Mon, Dec 7, 2009 at 2:05 PM, Diederick Stoffers <d.stoffers@gmail.com>

> wrote:

>

> Hi,

>

> We have a new 24-core Dell PowerEdge R905 server with 128GB's RAM. The 64

>

> bits version of Fedora 12 lists the correct amount of 128GB, CentOS only

>

> finds 32GB (and so does Scientific Linux). I would much prefer to use CentOS

>

> (most of the software we use is specifically designed for CentOS). Does

>

> anyone know what is causing this/how to fix it?

>

> Many Thanks,

>

> Diederick

From:http://www.redhat.com/docs/manuals/enterprise/RHEL-5-manual/Virtualization-en-US/ch-virt-hw-support.html*

"The Red Hat Enterprise Linux Virtualization kernel does not support more than 32GB of memory for x86_64 systems. If you need to boot the virtualization kernel on systems with more than 32GB of physical memory installed, you must append the kernel command line with*mem=32G. This example shows how to enable the proper parameters in the*grub.conf*file:
title Red Hat Enterprise Linux Server (2.6.18-4.elxen)
root (hd0, 0)
kernel /xen.gz-2.6.18-4-el5 mem=32G
module /vmlinuz -2.6.18-4.el5xen ro root=LABEL=/
module /initrd-2.6.18-4.el5xen.img"
--
Jake Paulus
JakePaulus@gmail.com

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12-08-2009, 12:41 PM

On Mon, Dec 07, 2009 at 01:05:04PM +0100, Diederick Stoffers wrote:
> Hi,
> We have a new 24-core Dell PowerEdge R905 server with 128GB's RAM. The 64
> bits version of Fedora 12 lists the correct amount of 128GB, CentOS only
> finds 32GB (and so does Scientific Linux). I would much prefer to use
> CentOS (most of the software we use is specifically designed for CentOS).
> Does anyone know what is causing this/how to fix it?

Have you checked "xm info" to see the Xen hypervisor memory info?
Maybe it's just the dom0 linux kernel that doesn't have more than 32G,
and the Xen hypervisor sees all of it.

Anyways, you should always limit dom0 memory to 512 MB or 1 GB to disable
Xen memory ballooning.

If you boot dom0 with all the (32G of) memory visible to it, and then
create VMs, and thus balloon dom0 down to much smaller amount of memory,
you'll get all kinds of problems when the dom0 linux memory suddenly is
much smaller than it was during boot time.

You should always limit and dedicate some amount of memory to dom0.
Use dom0_mem=1G option for xen.gz in grub.conf.

-- Pasi

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