[OpenIndiana-discuss] KVM on Illumos / Xen support

[Pasi Kärkkäinen]

On Thu, Aug 18, 2011 at 09:38:19PM +0200, Nikola M wrote:
> Dave Koelmeyer wrote:
> > For those that haven't already seen:
> >
> > http://dtrace.org/blogs/bmc/2011/08/15/kvm-on-illumos/???
> I would like to know, now that is KVM here in Illumos
> (and presumably in OpenIndiana and when also AMD CPU support is written,
> beside Intel support),
> does that means we have something more powerful than XEN is?
> 

Depends how you define 'powerful' :) 
Architecture in Xen is quite different from KVM.. 

Xen has:
	- Thin hypervisor (around 2MB in size) - much less code than OS kernel
	- Thin interfaces between domains (VMs)
	- Strong isolation between domains
	- "Xen driver domains" -concept: virtual net/disk backends for VMs don't need to be in dom0, 
	  backends can be served from special driver domain VMs! Making the system disaggregated and very secure.


> I do not know if all Joyent's upgrades they made to illumos
> (ZFS disk bandwith for zones, etc) ends up inside Illumos?
> 
> Since Oracle left working Xen in S11Ex for 64-bit x86 host but is
> pushing it's closed Xen implementation
> and Xen support is currently not quite maintained in
> Illumos/OpenIndiana, maybe KVM is what one could use (beside Virtualbox).
> 

Yep, that's the problem.. Xen support in Illumos/Openindiana needs some work.

	- Someone should upstream the XVM hypervisor patches to upstream Xen hypervisor
		- so you could use the stock Xen hypervisor in Illumos in the future

	- Someone should make sure the Illumos/OpenIndiana kernel properly runs as Xen dom0
		- Bugfixing, testing and maintenance in general needed

	- Someone should make sure Illumos/OpenIndiana kernel properly runs with PV drivers as Xen HVM guest

That will be some work, yes, but the good thing is that it is (and has been) already working in OpenSolaris.. 


Example of Xen Driver Domains:

	- Run Xen with Linux dom0 (or Illumos dom0, if someone starts working on Illumos Xen support).
	- Create Illumos/OpenIndiana VM (Xen HVM probably to take advantage of CPU hardware virtualization and EPT)
	- Use Xen PCI passthru to pass disk controller (HBA) to the Illumos/OpenIndiana VM
	- Run ZFS in the Illumos/Openindiana VM, with direct access to the HBA and disks.
	- Make sure the Xen backend-drivers from OpenSolaris run properly in Illumos/OpenIndiana, and run them.
	- Serve disk backends to other VMs from the Illumos/OpenIndiana driver domain from ZFS!

That would be very interesting setup!

-- Pasi