RE: [Xen-users] Using Linux 2.4 custom domu on x86_64 2.6 Xen dom0

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Brian
> Sent: 24 July 2006 18:50
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-users] Using Linux 2.4 custom domu on x86_64 
> 2.6 Xen dom0
> 
> Hi group,
> 
> I have searched the archives and found some clues to making 
> this work, but all is not clear yet. 
> 
> Here's what I need to do:
> Run 10 domu's using custom Linux 2.4.27 kernel with a number 
> of patches on a Xen dom0. Each server in our current non-Xen 
> environment requires 1GB ram, and I am assuming about the 
> same usage in a Xen environment plus a bit of overhead.

The math here is fine. 
> 
> 
> Here's the hardware/base system I'm using:
> Dell 1855 blade servers Dual 3.0ghz 12GB ram. These can run 
> either x86 32-bit, or x86_64. The base system is CentOS 4.3.
> 
> 
> Where I'm at:
> 1) I figure 10 domu's should run on each blade depending on 
> the final overhead of the Xen system. 
> 2) I believe Xen 3.x is not an option as there is no current 
> port of a Linux 2.4 domu Kernel. Am I right that only Linux 
> 2.6 is ported to Xen 3.x for domu?
> 3) To use more than 4GB ram, it looks like I have to use 
> either xen-unstable-install-x86_32p.tgz (PAE >4GB support), 
> or xen-unstable-install-x86_64.tgz (since Xen 3.x is probably 
> not an option), depending on the base system I run (eg. 
> Cenos4.3 x86 or x86_64).
> 
> Big question:
> How do I make 2.4.27 kernel with my patches Xenified for domu 
> use in xen-unstable-install-x86_x? 
> 
> In the xen-2.0.7-src.tgz file, I see there is a 
> linux-2.4.30-xen-sparse directory. Do I have to add my 
> patches to a vanilla 2.4.30 kernel, then compile it somehow 
> under the Xen source tree? Can I drop my current 2.4.27 
> sources into the Xen tree, then compile and smile?

Theoretically this will work. However, the Xen 2.x and Xen 3.x are
different API's, and thus you will not be able to run your 2.x kernel on
3.x. Not even the slightest chance - it's blocked. And even if it wasn't
blocked, it's not compatible enough to even have a chance of working... 

Since you want to run more than 4 1GB DomU on one guest (presumably to
save hardware cost), I can't really see any way to solve this, as Xen
2.x doesn't support PAE or x86_64. 

The only viable solutions are:
1. Upgrade your kernel to 2.6.16 or so, and apply the relevant patches
here. 
2. Run fully virtualized (VT/SVM technology) on x86_64 or 32-bit PAE. 
3. Run fewer guest per blade (possibly on a less expensive blade-model
with fewer cores/CPU's and less memory slots).

--
Mats

> 
> 
> Any help at all would be appreciated.
> 
> Brian
> 
> 
> 
> 
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