[CentOS-virt] i386 VM on x86_64 host in Xen

Tue Dec 11 16:27:00 UTC 2007
Scott Dowdle <dowdle at montanalinux.org>


----- "Karanbir Singh" <mail-lists at karan.org> wrote:
> apart from mass scale hosting solutions, I am yet to see a role where
> openvz actually provided a better all around VM solution than Xen.

Depends on your definition of better.  One that works (for example the discussion you are having now about problems running i386 guests on x86_64 hosts) might fall into that. :)

But seriously, it's all about meeting the needs of the users... and there is a large variety of virtualization needs out there... and not a single, one size fits all best solution.  I'm not trying to badmouth Xen and I'd appreciate it if people didn't badmouth other solutions either.

There are uses where Xen is much better suited and OpenVZ isn't even a viable option.  But there are other cases where OpenVZ is a better fit especially with regards to density and scalability.  OpenVZ is also very attractive in those situations where you want to isolate a single or a small number of services... although the vast majority if my deployments have a full set of services.

> Even  the management tools and the developer support behind Xen far out 
> weights that on openvz.

I'm not sure what you mean by that.  OpenVZ comes from Virtuozzo which has been out over 6 years now and has been deployed by thousands (if not tens of thousands) of deployments.

The OpenVZ developers (along with a few from IBM and Google mostly) are currently working on getting "control group" features in the mainline kernel... and that is expected to happen between now and the next 12-18 months.  Who knows how the mainline implementation will differ from the stock OpenVZ?

So far as management tools go, I wondering what management tools you use for Xen.  The only one I've really tried was Virtual Machine Manager and prior to the most recent release in 5.1, it couldn't even START a virtual machine.  I've tested out XenSource's management solution and while it has a few more features that Virtual Machine Manager, there still isn't much there.

Given the 20ish resource parameters provided by OpenVZ and the vzctl command where all of those resources can be dynamically changed... and looking at /proc/user_beancounters on the hn or guests is the most direct way to monitor them... those rudimentary cli tools seem more up to the task than the current crop of GUI tools I see for Xen.  Although perhaps I'm just ignorant of additional management programs that are out there... and I look forward to you informing me.

The good thing is Red Hat has taken a virtualization agnostic approach with their tools and with some additional development work, they could support OpenVZ too.  I believe someone added OpenVZ support to libvirt this past summer but I don't know how complete it was nor if it got integrated into upstream or not.

> And for those mass hosting solutions, a bit of security minded setups would remove the need 
> to have this sort of a virtual userspace  virtualising anyway.

I'm not really sure what you mean, please clarify.

Scott Dowdle
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