Re: [Xen-users] 32bit or 64bit dom0?

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Tue, Jan 26, 2010 at 12:58:33AM +0100, iS-Fun Internet Services GmbH, Holger 
Diehm wrote:
> Hello,
> 
> your question is just right for me to tell about my experiences of the last 
> two weeks, when I migrated some older xen Dom0 installs to newer xen 
> versions.
> I can only talk about pv, because thats the only thing we need (atm).
> First I set up two new 64bit Dom0 Debian servers. Compilation of xen 3.4.2 
> from source worked fine.ocumentation set aside - I don't need it.
> I directly booted into an 2.6.31.12 xenified kernel - 64 bit - this kernel so 
> far works like a charm - search the list for the patches for 2.6.31.
> 
> The 2.6.18.8 Kernel from the xen-mercurial tree was built for some legacy 
> DomU-32bit-Systems, which threw me libsysfs Errors on boot (some earlier 
> SuSes) - works as expected too :-)
> 
> These legacy Systems were on a xen 2.0.x and have to run on for some more 
> time, the "newer"  were migrated from xen 3.0.x.
> 
> As you can see, just any paravirtualized DomU - 32 or 64 bit run on that 
> 64bit 
> xen-Dom0 just fine.
> I booted in various GNU/Linux system-flavours just swapping my xenified 
> kernel 
> with the distribution-kernel - centos,SuSe,debian,gentoo.
> The interesting point is, that a recent 32bit DomU even runs with the 
> 64bit-Kernel - but very soon I decided to build an extra 32bit DomU-kernel, 
> just to not confuse any tool that depends on the arch reported by the 
> kernel - build tools etc can be easily confused by a wrong "uname".
> 
> So I have three different kernels - 2.6.31.12Dom[0U]64bit, 2.6.31.12DomU 32 
> bit an 2.6.18.8DomU 32 bit - all 32bit Kernels are PAE-enabled.
> I ran several tests and there is just nothing ugly to report :-)
> 32 bit VMs run alongside 64 bit VMs, no Problems.
> 
> The basics are reported everywhere - old xens allowed to have the tty1 as 
> console . Rename all tty1 to xvc0... see inittab, securetty, and settings for 
> console in the DomU configuration, if you haven't already.
> Perhaps create the device under /dev - if not available.
> If you use filebased Images, switch from file: to tap:aio: in your DomU 
> config 
> file. It works well and you don't run into any loop-device issues.
> 
> What I often thought is a mistake, was my helping-hand with those 
> old "unportable" DomUs...the "ancient" but still maintained 2.6.18.8 kernel 
> from xen-mercurial.
> None of them ole DomUs ran with a recent kernel !
> That is perhaps one thing you should *really* take into account for your 
> Upgrade - test the DomUs with the newer Kernels you plan to use, and if you 
> run into troubles, look for a matching xenified-kernel.
> This made it a nice job for me to migrate old xen DomUs to newer versions.
> 
> So I couldn't tell you the route to take, but perhaps some of the 
> above "signs" help yout to take your route "your way".
> 
> So thanks to all the guys who feel responsible to push xen forward..not only 
> to newer kernels :-) And to all the unnamed contributors.
> 

Good to hear it worked OK :)

I think there's still one Xen 2.0.x server running that I've installed.. it has 
been very stable:)

-- Pasi


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