More then 16GB with FC6 or FC7?

[thewird]

Is there any way to make the xen kernel see more then
16GB of ram when its installed on a 32bit OS (either
FC6 or FC7)?

I tried FC7 64bit since it can see all the ram,
however the only 32bit OS I was able to install
successfully was windows XP. Every other distro (FC6,
FC7, and CentOS 4.5 & 5.0) would freeze up at some
point in the installation or bootup section.

I have a machine with 28GB of ram and have a month to
get it running.

Marco Jorge

[Daniel P. Berrange]

On Wed, Jun 27, 2007 at 05:00:13AM -0400, thewird wrote:
>  Is there any way to make the xen kernel see more then
>  16GB of ram when its installed on a 32bit OS (either
>  FC6 or FC7)? 
No it is an architectural limitation of Xen that 32-bit is limited to
a maximum of 16 GB, even with PAE.

>  I tried FC7 64bit since it can see all the ram,
>  however the only 32bit OS I was able to install
>  successfully was windows XP. Every other distro (FC6,
>  FC7, and CentOS 4.5 & 5.0) would freeze up at some
>  point in the installation or bootup section.
>  
>  I have a machine with 28GB of ram and have a month to
>  get it running. 
64-bit is the way to go. Try toggleing the 'acpi' and 'apic' settings
for the HVM guests as this often helps with lockups.

Dan.
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[Gerd Hoffmann]

Daniel P. Berrange wrote:
>  On Wed, Jun 27, 2007 at 05:00:13AM -0400, thewird wrote:
> > Is there any way to make the xen kernel see more then
> > 16GB of ram when its installed on a 32bit OS (either
> > FC6 or FC7)?
>  
>  No it is an architectural limitation of Xen that 32-bit is limited to
>  a maximum of 16 GB, even with PAE. 
Well, there is one from the dirty tricks department:  Install 32bit fc7, 
pull 64bit xen kernel from the 64bit kernel-xen rpm, boot that with the 
32bit linux kernel.

Mixing 32bit and 64bit guests isn't going to work for the time being 
(needs a kernel update).  But with the 64bit hypervisor underneath the 
system should be able use all memory, even with 32bit guests only.

cheers,
   Gerd