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

["Ian Tobin" <itobin@xxxxxxxxxxxxx>]

Thanks for the info guys, ive been playing with 3.4.2 on 32bits but im thinking 
for the future it would be worth having 64bits for things like win2008R2 as 
this is 64 bit only.

Ill build a new server and do some tests :)

Many thanks

Ian



-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Pasi Kärkkäinen
Sent: 26 January 2010 07:28
To: iS-Fun Internet Services GmbH, Holger Diehm
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] 32bit or 64bit dom0?

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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