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RE: [Xen-users] RHEL 5.2 Xen Kernel doesn't detect all amount of physical memory



It seems unlikely that this is related, but see this bugzilla:
https://bugzilla.redhat.com/show_bug.cgi?id=250299
I had this problem in F7, F8 (apparently it still exists in F9 as well),
CentOS 5.2, and maybe CentOS 5.3 (probably exists there, but I don't
remember if I've tried it).
In each case where I experienced the issue, the patch for grub solved the
problem.
This issue only seems to happen on certain BIOSes, and even then the stock
kernels work fine, but the Xen ones don't.
The reason I doubt it is related is I haven't tried it on PAE, only x86_64,
and I believe the memory was limited to 3.2 GiB, not 14 like your issue.
However, I figured I'd mention this in case you have the same problem
(probably 3.2 GiB vs 14) when you go to x86_64 and find the patch solves it
(or in case you feel bold and daring and try it even where it seems
unrelated and find it to work).  Mentioning it to the support guy might get
it fixed upstream (since bugzilla reports for F7, F8, and F9 haven't to the
best of my knowledge), though it seems like bugzilla should do that if it
were going to be fixed upstream at all.
        Dustin

-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Ido Levy
Sent: Thursday, August 28, 2008 07:58
To: Robert Dunkley
Cc: tom.ashley@xxxxxxxxx; Xen-users@xxxxxxxxxxxxxxxxxxx;
xen-users-bounces@xxxxxxxxxxxxxxxxxxx
Subject: RE: [Xen-users] RHEL 5.2 Xen Kernel doesn't detect all amount of
physical memory

Hi,

Thank you all for your replies.

The reason I brought up this issue is that currently I have a machine with
64GB RAM installed with RHEL 5.2 i386 version.
When using the PAE kernel the OS detects the total amount of memory, but
when using the Xen kernel that shipped with this Red Hat distribution it
detects only 14GB of RAM

I was wondering if I will install the x86_64 version of RHEL 5.2 will it
detects more memory.

Any help figure out what is the issue will be appreciated.
In addition I would be happy to provide the info to the guy from the Red
Hat support team.

Thanks

Ido



                                                                           
             "Robert Dunkley"                                              
             <Robert@xxxxxxxxx                                             
             >                                                          To 
             Sent by:                  <tom.ashley@xxxxxxxxx>              
             xen-users-bounces                                          cc 
             @lists.xensource.         Xen-users@xxxxxxxxxxxxxxxxxxx       
             com                                                   Subject 
                                       RE: [Xen-users] RHEL 5.2 Xen Kernel 
                                       doesn't detect all                  
             08/28/2008 02:24          amountofphysical memory             
             PM                                                            
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           




Hi,

I got a reply from RedHat support (Only emailed poster and not the list
initially). Max for RHEL Xen kernel is same as standard Kernel (1Tb for
X64) but max mem per VM is limited to 32Gb.

Reassuring to hear though, I was a bit worried that updating our Centos
5.2 systems from 32Gb Ram to 128Gb might not work :)


Rob

-----Original Message-----
From: tom.ashley@xxxxxxxxx [?mailto:tom.ashley@xxxxxxxxx]
Sent: 28 August 2008 12:15
To: Robert Dunkley; xen-users-bounces@xxxxxxxxxxxxxxxxxxx; Ido Levy
Cc: Xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] RHEL 5.2 Xen Kernel doesn't detect all
amountofphysical memory

Bog standard out of the box, I have a 64 bit centos 5.2 holding and
recognising 64GB RAM happily. RHEL should be able to do the same.
Sent using BlackBerry(r) from Orange

-----Original Message-----
From: "Robert Dunkley" <Robert@xxxxxxxxx>

Date: Thu, 28 Aug 2008 10:07:33
To: Ido Levy<IDOL@xxxxxxxxxx>
Cc: <Xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-users] RHEL 5.2 Xen Kernel doesn't detect all amount
             ofphysical memory


>From what I have read the XenServer distribution can support up to 32GB
RAM per VM and 128GB for the whole system.

My guess is that unless a deliberate restriction is put in place the
limits RAM for RHEL5 Xen kernel then 256Gb RAM in total and 32Gb RAM per
VM is probably the max.

Anyone know for sure?

-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
[?mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Ido Levy
Sent: 28 August 2008 09:54
To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] RHEL 5.2 Xen Kernel doesn't detect all amount
ofphysical memory


Hello All,

Does anyone know what is the current status of RHEL 5.2 x86_64 with
respect
to the maximum amount of RAM detected by the Xen 64 bit kernel
(the one that shipped with Red Hat distribution )

In the following link
https://www.redhat.com/docs/manuals/enterprise/RHEL-5-manual/en-US/RHEL5
10/Virtualization_Guide/ch-virt-hw-support.html
it states that 32GB of RAM is the maximum amount of physical memory the
Xen
kernel can detect. Is it still the updated status ?

Is there a work around or any other way to overcome this limit ?

Any info would be appreciated

Thanks,

Ido


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